0000868857-26-000018 | 11-K | XBRL Viewer

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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The entire disclosure for master trust arrangement in which employee stock purchase, saving, or similar plan (employee benefit plan (EBP)) participates.

INVESTMENT IN AECOM DC RETIREMENT PLANS SMA MASTER TRUST

12 Months Ended

Dec. 31, 2025

INVESTMENT IN AECOM DC RETIREMENT PLANS SMA MASTER TRUST


D.			INVESTMENT IN AECOM DC RETIREMENT PLANS VANGUARD MASTER TRUST

The following table presents the net assets of the Vanguard Master Trust as of December 31:


	Vanguard Master Trust
	2025		2024
	(expressed in thousands)
Investments at fair value
Collective investment trusts (measured at NAV)	$	3,413,123	$	2,734,006
Mutual funds	—		630,038

Net assets of Vanguard Master Trust	$	3,413,123	$	3,364,044

The following table shows the changes in net assets for the Vanguard Master Trust for the year ended December 31:


	2025
	(expressed in thousands)
Change in net assets:
Net appreciation in fair value of investments	$	532,759
Interest and dividend income	4
Total investment income	532,763

Net purchases (redemptions)	(482,636)
Administrative expenses	(1,048)

Net increase in net assets	49,079



Net assets:
Beginning of year	3,364,044
End of year	$	3,413,123


	As of December 31, 2024
	Quoted Prices in Active Markets for Identical Assets (Level 1)		Significant Observable Inputs (Level 2)		Total Fair Value
	(expressed in thousands)
Mutual funds	$	630,038	$	—	$	630,038
Total investments in the fair value hierarchy	$	630,038	$	—	$	630,038

Investments measured at NAV					2,734,006
Total investments at fair value					$	3,364,044

Net Asset Value per Share — The following tables summarize investments measured at NAV per share as of December 31, 2025 and 2024, respectively:

December 31, 2025

Fair Value

Unfunded Commitment

Redemption Frequency (if Currently Eligible)

Other Redemption Restrictions

Redemption Notice Period

(expressed in thousands)

Retirement date funds

2,016,233

—

Daily

None

Index funds

1,396,890

—

Daily

None

December 31, 2024

Fair Value

Unfunded Commitment

Redemption Frequency (if Currently Eligible)

Other Redemption Restrictions

Redemption Notice Period

(expressed in thousands)

Retirement date funds

1,503,727

—

Daily

None

Index funds

1,230,279

—

Daily

None


E.			INVESTMENT IN AECOM DC RETIREMENT PLANS SMA MASTER TRUST

The following table presents the net assets of the SMA Master Trust as of December 31:


	SMA Master Trust
	2025		2024
	(expressed in thousands)
Investments at fair value
Stocks	$	—	$	269,919
Government bonds	68,339		48,545
Corporate bonds	86,656		74,084
Mortgage-backed securities	58,570		53,807
Asset-backed securities	6,733		6,144
Collective investment trusts	401,232		257,107
Cash and cash equivalents	4,822		8,610
	626,352		718,216
Accounts receivable
Receivable for securities sold	328		596
Accrued income	1,764		1,631
Other	515		514
	2,607		2,741
Accounts payable
Due to broker for securities purchased	(3,759)		(2,538)
Operating payables	(143)		(768)
	(3,902)		(3,306)

Net assets of SMA Master Trust	$	625,057	$	717,651

The following table shows the changes in net assets for the SMA Master Trust for the year ended December 31:


	2025
	(expressed in thousands)
Change in net assets:
Net appreciation in fair value of investments and income	$	150,726

Net purchases (redemptions)	(243,199)
Administrative expenses	(121)

Net decrease in net assets	(92,594)



Net assets:
Beginning of year	717,651
End of year	$	625,057

The following tables set forth by level, within the fair value hierarchy, the SMA Master Trust assets at fair value as of December 31, 2025 and 2024:


	As of December 31, 2025
	Quoted Prices in Active Markets for Identical Assets (Level 1)		Significant Observable Inputs (Level 2)		Total Fair Value
	(expressed in thousands)
Fixed income instruments:
Asset-backed securities	$	—	$	6,733	$	6,733
Mortgage-backed securities	—		58,570		58,570
Corporate bonds	—		86,656		86,656
Government bonds	—		68,339		68,339
Stocks	—		—		—
Cash and cash equivalents	4,822		—		4,822
Total investments at fair value	$	4,822	$	220,298	225,120

Investments measured at NAV					401,232
Total investments at fair value					$	626,352


	As of December 31, 2024
	Quoted Prices in Active Markets for Identical Assets (Level 1)		Significant Observable Inputs (Level 2)		Total Fair Value
	(expressed in thousands)
Fixed income instruments:
Asset-backed securities	$	—	$	6,144	$	6,144
Mortgage-backed securities	—		53,807		53,807
Corporate bonds	—		74,084		74,084
Government bonds	—		48,545		48,545
Stocks	269,919		—		269,919
Cash and cash equivalents	8,610		—		8,610
Total investments at fair value	$	278,529	$	182,580	461,109

Investments measured at NAV					257,107
Total investments at fair value					$	718,216

Net Asset Value per Share — The following table summarizes investments measured at NAV per share as of December 31, 2025 and 2024:

December 31, 2025

Fair Value

Unfunded Commitment

Redemption Frequency (if Currently Eligible)

Other Redemption Restrictions

Redemption Notice Period

(expressed in thousands)

Arrowstreet International Equity Fund

383,294

—

Daily

None

Northern Trust All Country World ex-U.S. Index Fund

17,938

—

Daily

None

December 31, 2024

Fair Value

Unfunded Commitment

Redemption Frequency (if Currently Eligible)

Other Redemption Restrictions

Redemption Notice Period

(expressed in thousands)

Arrowstreet International Equity Fund

253,548

—

Daily

None

Northern Trust All Country World ex-U.S. Index Fund

3,559

—

Daily

None


F.			INVESTMENT IN AECOM DC RETIREMENT PLANS STABLE VALUE MASTER TRUST

The following table presents the net assets of the Stable Value Master Trust as of December 31:


	Stable Value Master Trust
	2025		2024
	(expressed in thousands)
Investments measured at NAV
Collective investment trust	$	313,784	$	323,734

Net assets of Stable Value Master Trust	$	313,784	$	323,734

The following table shows the changes in net assets for the Stable Value Master Trust for the year ended December 31:


	2025
	(expressed in thousands)
Change in net assets:
Interest and dividend income	$	9,273

Net purchases (redemptions)	(19,214)
Administrative expenses	(9)

Net decrease in net assets	(9,950)



Net assets:
Beginning of year	323,734
End of year	$	313,784

Net Asset Value per Share — The following table summarizes investments measured at NAV per share as of December 31, 2025 and 2024:

December 31, 2025

Fair Value

Unfunded Commitment

Redemption Frequency (if Currently Eligible)

Other Redemption Restrictions

Redemption Notice Period

(expressed in thousands)

Stable value fund

313,784

—

Daily

None

December 31, 2024

Fair Value

Unfunded Commitment

Redemption Frequency (if Currently Eligible)

Other Redemption Restrictions

Redemption Notice Period

(expressed in thousands)

Stable value fund

323,734

—

Daily

None

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

The entire disclosure for master trust arrangement in which employee stock purchase, saving, or similar plan (employee benefit plan (EBP)) participates.

INVESTMENT IN AECOM DC RETIREMENT PLANS SMA MASTER TRUST (Details) - EBP 055 - USD ($) $ in Thousands	Dec. 31, 2025	Dec. 31, 2024
EBP, Master Trust [Line Items]
Investments at fair value	$ 7,291,530	$ 6,704,959
Other	668	561
Total receivables	76,971	73,890
Accrued expenses	(71)	(223)
Total liabilities	(234)	(291)
Net assets available for benefits per the financial statements	$ 7,368,267	6,778,558
SMA Master Trust
EBP, Master Trust [Line Items]
Plan's interest in Master Trust (percent)	100.00%
Master Trust \| SMA Master Trust
EBP, Master Trust [Line Items]
Investments at fair value	$ 626,352	718,216
Receivable for securities sold	328	596
Accrued income	1,764	1,631
Other	515	514
Total receivables	2,607	2,741
Due to broker for securities purchased	(3,759)	(2,538)
Accrued expenses	(143)	(768)
Total liabilities	(3,902)	(3,306)
Net assets available for benefits per the financial statements	625,057	717,651
Master Trust \| SMA Master Trust \| Total Fair Value
EBP, Master Trust [Line Items]
Investments at fair value	225,120	461,109
Master Trust \| SMA Master Trust \| Level 1
EBP, Master Trust [Line Items]
Investments at fair value	4,822	278,529
Master Trust \| SMA Master Trust \| Level 2
EBP, Master Trust [Line Items]
Investments at fair value	220,298	182,580
Master Trust \| SMA Master Trust \| Investments measured at NAV
EBP, Master Trust [Line Items]
Investments at fair value	401,232	257,107
Master Trust \| SMA Master Trust \| Stocks
EBP, Master Trust [Line Items]
Investments at fair value	0	269,919
Master Trust \| SMA Master Trust \| Stocks \| Total Fair Value
EBP, Master Trust [Line Items]
Investments at fair value	0	269,919
Master Trust \| SMA Master Trust \| Stocks \| Level 1
EBP, Master Trust [Line Items]
Investments at fair value	0	269,919
Master Trust \| SMA Master Trust \| Stocks \| Level 2
EBP, Master Trust [Line Items]
Investments at fair value	0	0
Master Trust \| SMA Master Trust \| Government bonds
EBP, Master Trust [Line Items]
Investments at fair value	68,339	48,545
Master Trust \| SMA Master Trust \| Government bonds \| Total Fair Value
EBP, Master Trust [Line Items]
Investments at fair value	68,339	48,545
Master Trust \| SMA Master Trust \| Government bonds \| Level 1
EBP, Master Trust [Line Items]
Investments at fair value	0	0
Master Trust \| SMA Master Trust \| Government bonds \| Level 2
EBP, Master Trust [Line Items]
Investments at fair value	68,339	48,545
Master Trust \| SMA Master Trust \| Corporate bonds
EBP, Master Trust [Line Items]
Investments at fair value	86,656	74,084
Master Trust \| SMA Master Trust \| Corporate bonds \| Total Fair Value
EBP, Master Trust [Line Items]
Investments at fair value	86,656	74,084
Master Trust \| SMA Master Trust \| Corporate bonds \| Level 1
EBP, Master Trust [Line Items]
Investments at fair value	0	0
Master Trust \| SMA Master Trust \| Corporate bonds \| Level 2
EBP, Master Trust [Line Items]
Investments at fair value	86,656	74,084
Master Trust \| SMA Master Trust \| Mortgage-backed securities
EBP, Master Trust [Line Items]
Investments at fair value	58,570	53,807
Master Trust \| SMA Master Trust \| Mortgage-backed securities \| Total Fair Value
EBP, Master Trust [Line Items]
Investments at fair value	58,570	53,807
Master Trust \| SMA Master Trust \| Mortgage-backed securities \| Level 1
EBP, Master Trust [Line Items]
Investments at fair value	0	0
Master Trust \| SMA Master Trust \| Mortgage-backed securities \| Level 2
EBP, Master Trust [Line Items]
Investments at fair value	58,570	53,807
Master Trust \| SMA Master Trust \| Asset-backed securities
EBP, Master Trust [Line Items]
Investments at fair value	6,733	6,144
Master Trust \| SMA Master Trust \| Asset-backed securities \| Total Fair Value
EBP, Master Trust [Line Items]
Investments at fair value	6,733	6,144
Master Trust \| SMA Master Trust \| Asset-backed securities \| Level 1
EBP, Master Trust [Line Items]
Investments at fair value	0	0
Master Trust \| SMA Master Trust \| Asset-backed securities \| Level 2
EBP, Master Trust [Line Items]
Investments at fair value	6,733	6,144
Master Trust \| SMA Master Trust \| Northern Trust Collective Short-term Investment Fund
EBP, Master Trust [Line Items]
Investments at fair value	401,232	257,107
Master Trust \| SMA Master Trust \| Cash and cash equivalents
EBP, Master Trust [Line Items]
Investments at fair value	4,822	8,610
Master Trust \| SMA Master Trust \| Cash and cash equivalents \| Total Fair Value
EBP, Master Trust [Line Items]
Investments at fair value	4,822	8,610
Master Trust \| SMA Master Trust \| Cash and cash equivalents \| Level 1
EBP, Master Trust [Line Items]
Investments at fair value	4,822	8,610
Master Trust \| SMA Master Trust \| Cash and cash equivalents \| Level 2
EBP, Master Trust [Line Items]
Investments at fair value	0	0
Master Trust \| SMA Master Trust \| Arrowstreet International Equity Fund
EBP, Master Trust [Line Items]
Investments at fair value	383,294	253,548
Unfunded Commitment	0	0
Master Trust \| SMA Master Trust \| Northern Trust All Country World ex-U.S. Index Fund
EBP, Master Trust [Line Items]
Investments at fair value	17,938	3,559
Unfunded Commitment	0	0
Plan interest in Master Trust \| SMA Master Trust
EBP, Master Trust [Line Items]
Investments at fair value	626,352	718,216
Receivable for securities sold	328	596
Accrued income	1,764	1,631
Other	515	514
Total receivables	2,607	2,741
Due to broker for securities purchased	(3,759)	(2,538)
Accrued expenses	(143)	(768)
Total liabilities	(3,902)	(3,306)
Net assets available for benefits per the financial statements	625,057	717,651
Plan interest in Master Trust \| SMA Master Trust \| Total Fair Value
EBP, Master Trust [Line Items]
Investments at fair value	225,120	461,109
Plan interest in Master Trust \| SMA Master Trust \| Level 1
EBP, Master Trust [Line Items]
Investments at fair value	4,822	278,529
Plan interest in Master Trust \| SMA Master Trust \| Level 2
EBP, Master Trust [Line Items]
Investments at fair value	220,298	182,580
Plan interest in Master Trust \| SMA Master Trust \| Investments measured at NAV
EBP, Master Trust [Line Items]
Investments at fair value	401,232	257,107
Plan interest in Master Trust \| SMA Master Trust \| Stocks
EBP, Master Trust [Line Items]
Investments at fair value	0	269,919
Plan interest in Master Trust \| SMA Master Trust \| Stocks \| Total Fair Value
EBP, Master Trust [Line Items]
Investments at fair value	0	269,919
Plan interest in Master Trust \| SMA Master Trust \| Stocks \| Level 1
EBP, Master Trust [Line Items]
Investments at fair value	0	269,919
Plan interest in Master Trust \| SMA Master Trust \| Stocks \| Level 2
EBP, Master Trust [Line Items]
Investments at fair value	0	0
Plan interest in Master Trust \| SMA Master Trust \| Government bonds
EBP, Master Trust [Line Items]
Investments at fair value	68,339	48,545
Plan interest in Master Trust \| SMA Master Trust \| Government bonds \| Total Fair Value
EBP, Master Trust [Line Items]
Investments at fair value	68,339	48,545
Plan interest in Master Trust \| SMA Master Trust \| Government bonds \| Level 1
EBP, Master Trust [Line Items]
Investments at fair value	0	0
Plan interest in Master Trust \| SMA Master Trust \| Government bonds \| Level 2
EBP, Master Trust [Line Items]
Investments at fair value	68,339	48,545
Plan interest in Master Trust \| SMA Master Trust \| Corporate bonds
EBP, Master Trust [Line Items]
Investments at fair value	86,656	74,084
Plan interest in Master Trust \| SMA Master Trust \| Corporate bonds \| Total Fair Value
EBP, Master Trust [Line Items]
Investments at fair value	86,656	74,084
Plan interest in Master Trust \| SMA Master Trust \| Corporate bonds \| Level 1
EBP, Master Trust [Line Items]
Investments at fair value	0	0
Plan interest in Master Trust \| SMA Master Trust \| Corporate bonds \| Level 2
EBP, Master Trust [Line Items]
Investments at fair value	86,656	74,084
Plan interest in Master Trust \| SMA Master Trust \| Mortgage-backed securities
EBP, Master Trust [Line Items]
Investments at fair value	58,570	53,807
Plan interest in Master Trust \| SMA Master Trust \| Mortgage-backed securities \| Total Fair Value
EBP, Master Trust [Line Items]
Investments at fair value	58,570	53,807
Plan interest in Master Trust \| SMA Master Trust \| Mortgage-backed securities \| Level 1
EBP, Master Trust [Line Items]
Investments at fair value	0	0
Plan interest in Master Trust \| SMA Master Trust \| Mortgage-backed securities \| Level 2
EBP, Master Trust [Line Items]
Investments at fair value	58,570	53,807
Plan interest in Master Trust \| SMA Master Trust \| Asset-backed securities
EBP, Master Trust [Line Items]
Investments at fair value	6,733	6,144
Plan interest in Master Trust \| SMA Master Trust \| Asset-backed securities \| Total Fair Value
EBP, Master Trust [Line Items]
Investments at fair value	6,733	6,144
Plan interest in Master Trust \| SMA Master Trust \| Asset-backed securities \| Level 1
EBP, Master Trust [Line Items]
Investments at fair value	0	0
Plan interest in Master Trust \| SMA Master Trust \| Asset-backed securities \| Level 2
EBP, Master Trust [Line Items]
Investments at fair value	6,733	6,144
Plan interest in Master Trust \| SMA Master Trust \| Northern Trust Collective Short-term Investment Fund
EBP, Master Trust [Line Items]
Investments at fair value	401,232	257,107
Plan interest in Master Trust \| SMA Master Trust \| Cash and cash equivalents
EBP, Master Trust [Line Items]
Investments at fair value	4,822	8,610
Plan interest in Master Trust \| SMA Master Trust \| Cash and cash equivalents \| Total Fair Value
EBP, Master Trust [Line Items]
Investments at fair value	4,822	8,610
Plan interest in Master Trust \| SMA Master Trust \| Cash and cash equivalents \| Level 1
EBP, Master Trust [Line Items]
Investments at fair value	4,822	8,610
Plan interest in Master Trust \| SMA Master Trust \| Cash and cash equivalents \| Level 2
EBP, Master Trust [Line Items]
Investments at fair value	0	0
Plan interest in Master Trust \| SMA Master Trust \| Arrowstreet International Equity Fund
EBP, Master Trust [Line Items]
Investments at fair value	383,294	253,548
Unfunded Commitment	0	0
Plan interest in Master Trust \| SMA Master Trust \| Northern Trust All Country World ex-U.S. Index Fund
EBP, Master Trust [Line Items]
Investments at fair value	17,938	3,559
Unfunded Commitment	$ 0	$ 0

RECONCILIATION OF FINANCIAL STATEMENTS TO FORM 5500 (Details) - EBP 055 - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2025	Dec. 31, 2024
EBP, Form 5500 Caption, Net Assets [Abstract]
Net assets available for benefits per the financial statements	$ 7,368,267	$ 6,778,558
Amounts allocated to withdrawing participants	(4,654)	(1,802)
Net assets available for benefits per Form 5500	7,363,613	$ 6,776,756
EBP, Form 5500 Caption, Benefit Payment and Payments to Provide Benefits [Abstract]
Net increase per financial statements	589,709
Net change in amounts allocated to withdrawing participants	(2,852)
Net increase per Form 5500	$ 586,857

Amount of asset less liability available to pay benefit of participant in employee stock purchase, saving, or similar plan (employee benefit plan (EBP)), including, but not limited to, aggregation of participants' individual account balances.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 962
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-Paragraph 8
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Reference 2: http://www.xbrl.org/2003/role/disclosureRef
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-Paragraph 1
-Subparagraph (b)(3)
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SCHEDULE OF ASSETS (HELD AT END OF YEAR) (Details) - EBP 055	12 Months Ended
	Dec. 31, 2025 USD ($) shares
EBP, Schedule of Asset Held for Investment [Line Items]
EIN	61-1088522
Plan number	055
Notes receivable from participants	$ 23,208,585
Total investments	2,962,774,084
AECOM Common Stock
EBP, Schedule of Asset Held for Investment [Line Items]
TOTAL PLAN INVESTMENTS	446,479,546
Registered Investment Companies:
EBP, Schedule of Asset Held for Investment [Line Items]
TOTAL PLAN INVESTMENTS	573,111,973
T. Rowe Structured Research
EBP, Schedule of Asset Held for Investment [Line Items]
TOTAL PLAN INVESTMENTS	1,400,227,423
Assets in Bank of America, N.A. Self-Directed Brokerage Accounts
EBP, Schedule of Asset Held for Investment [Line Items]
TOTAL PLAN INVESTMENTS	$ 519,746,557
Minimum
EBP, Schedule of Asset Held for Investment [Line Items]
Interest rate on participant loans (percent)	4.25%
Maximum
EBP, Schedule of Asset Held for Investment [Line Items]
Interest rate on participant loans (percent)	9.50%
Investment, Identifier [Axis]: Participation in common or collective trusts \| EARNEST Partners SMID Cap Core Fund
EBP, Schedule of Asset Held for Investment [Line Items]
TOTAL PLAN INVESTMENTS	$ 246,860,186
Plan investments held (in shares) \| shares	23,495,761
Investment, Identifier [Axis]: Participation in common or collective trusts \| Fidelity Growth Company Commingled Fund
EBP, Schedule of Asset Held for Investment [Line Items]
TOTAL PLAN INVESTMENTS	$ 568,253,219
Plan investments held (in shares) \| shares	6,382,716
Investment, Identifier [Axis]: Participation in common or collective trusts \| T.Rowe Structured Research
EBP, Schedule of Asset Held for Investment [Line Items]
TOTAL PLAN INVESTMENTS	$ 585,114,018
Plan investments held (in shares) \| shares	5,827,248
Investment, Identifier [Axis]: Registered Investment Companies \| BlackRock Advisors BIF Money Fund
EBP, Schedule of Asset Held for Investment [Line Items]
TOTAL PLAN INVESTMENTS	$ 4,733,927
Plan investments held (in shares) \| shares	4,733,927
Investment, Identifier [Axis]: Registered Investment Companies \| Dodge & Cox U.S. Equity
EBP, Schedule of Asset Held for Investment [Line Items]
TOTAL PLAN INVESTMENTS	$ 568,378,046
Plan investments held (in shares) \| shares	34,260,280

INVESTMENT IN AECOM DC RETIREMENT PLANS STABLE VALUE MASTER TRUST (Details) - EBP 055 - USD ($) $ in Thousands	Dec. 31, 2025	Dec. 31, 2024
EBP, Master Trust [Line Items]
Investments at fair value	$ 7,291,530	$ 6,704,959
Stable Value Master Trust
EBP, Master Trust [Line Items]
Plan's interest in Master Trust (percent)	100.00%
Master Trust \| Stable Value Master Trust
EBP, Master Trust [Line Items]
Investments at fair value	$ 313,784	323,734
Unfunded Commitment	0	0
Master Trust \| Collective investment trusts (measured at NAV) \| Investments measured at NAV \| Stable Value Master Trust
EBP, Master Trust [Line Items]
Investments at fair value	313,784	323,734
Plan interest in Master Trust \| Stable Value Master Trust
EBP, Master Trust [Line Items]
Investments at fair value	313,784	323,734
Unfunded Commitment	0	0
Plan interest in Master Trust \| Collective investment trusts (measured at NAV) \| Investments measured at NAV \| Stable Value Master Trust
EBP, Master Trust [Line Items]
Investments at fair value	$ 313,784	$ 323,734

INVESTMENT IN AECOM DC RETIREMENT PLANS VANGUARD MASTER TRUST (Details) - EBP 055 $ in Thousands	12 Months Ended
	Dec. 31, 2025 USD ($)
EBP, Change in Net Asset Available for Benefit, Increase (Decrease) from Income (Loss) on Investment [Abstract]
Net appreciation in fair value of investments and Investment gain from self-directed brokerage accounts	$ (48,300)
Interest and dividends	7,184
Net investment income	1,000,371
Beginning of year	6,778,558
End of year	7,368,267
Master Trust \| Vanguard Master Trust
EBP, Change in Net Asset Available for Benefit, Increase (Decrease) from Income (Loss) on Investment [Abstract]
Net appreciation in fair value of investments and Investment gain from self-directed brokerage accounts	532,759
Interest and dividends	4
Total investment income	532,763
Net purchases (redemptions)	(482,636)
Administrative expenses	(1,048)
Net investment income	49,079
Beginning of year	3,364,044
End of year	3,413,123
Plan interest in Master Trust \| Vanguard Master Trust
EBP, Change in Net Asset Available for Benefit, Increase (Decrease) from Income (Loss) on Investment [Abstract]
Net appreciation in fair value of investments and Investment gain from self-directed brokerage accounts	532,759
Interest and dividends	4
Total investment income	532,763
Net purchases (redemptions)	(482,636)
Administrative expenses	(1,048)
Net investment income	49,079
Beginning of year	3,364,044
End of year	$ 3,413,123

DESCRIPTION OF THE PLAN (Details) - EBP 055 - USD ($)	12 Months Ended
DESCRIPTION OF THE PLAN (Details) - EBP 055 - USD ($)	Dec. 31, 2025	Dec. 31, 2024
EBP, Description of Plan [Line Items]
Maximum annual participant pre-tax contribution rate, as percentage of compensation (percent)	75.00%
Participant automatic deferral rate (percent)	1.00%
Company's match (percent)	50.00%
Eligible compensation contributed by Participant that is matched (percent)	6.00%
Company's match allocation to participant's selected investment allocations (percent)	50.00%
Company's match allocation to AECOM common stock (percent)	50.00%
Participant vesting period in employer contributions	3 years
Forfeited non-vested accounts used to reduce future employer contributions and / or pay administrative expenses of the Plan	$ 1,200,000
EBP, Forfeited Nonvested Account	0	$ 0
Minimum loan amount	1,000
Participant loan limit	$ 50,000
Participant loan limit as a percentage of vested account balance (percent)	50.00%
Loan interest rate, spread on prime rate (percent)	1.00%
Minimum
EBP, Description of Plan [Line Items]
Interest rate on participant loans (percent)	4.25%
Loan repayment period (up to)	5 years
Maximum
EBP, Description of Plan [Line Items]
Interest rate on participant loans (percent)	9.50%
Loan repayment period (up to)	20 years

FAIR VALUE MEASUREMENTS (Tables)

12 Months Ended

Dec. 31, 2025

EBP, Investment, Fair Value and NAV [Line Items]

Schedule of Plan's Investments at Fair Value in Recurring Basis and the Plan's Investments at NAV per share

Below are the Plan’s investments carried at fair value on a recurring basis by the ASC 820-10 fair value hierarchy levels described in Note B:


	As of December 31, 2025
	Quoted Prices in Active Markets for Identical Assets (Level 1)		Significant Observable Inputs (Level 2)		Total Fair Value
	(expressed in thousands)
Mutual funds	$	573,112	$	—	$	573,112
AECOM common stock	446,480		—		446,480
Self-directed brokerage accounts	495,278		24,468		519,746
Total investments in the fair value hierarchy	$	1,514,870	$	24,468	$	1,539,338
Investments measured at NAV					1,400,228
Total investments at fair value					$	2,939,566


	As of December 31, 2024
	Quoted Prices in Active Markets for Identical Assets (Level 1)		Significant Observable Inputs (Level 2)		Total Fair Value
	(expressed in thousands)
Mutual funds	$	597,766	$	—	$	597,766
AECOM common stock	521,670		—		521,670
Self-directed brokerage accounts	430,682		24,356		455,038
Total investments in the fair value hierarchy	$	1,550,118	$	24,356	$	1,574,474
Investments measured at NAV					725,056
Total investments at fair value					$	2,299,530

Net Asset Value per Share — The following tables summarize investments measured at NAV per share as of December 31, 2025 and 2024:

December 31, 2025

Fair Value

Unfunded Commitment

Redemption Frequency (if Currently Eligible)

Other Redemption Restrictions

Redemption Notice Period

(expressed in thousands)

Fidelity Growth Company Commingled Fund

568,254

—

Daily

None

T. Rowe Price Structured Research Common Trust Fund

585,114

—

Daily

None

EARNEST Partners Emerging Market Fund

246,860

—

Daily

None

December 31, 2024

Fair Value

Unfunded Commitment

Redemption Frequency (if Currently Eligible)

Other Redemption Restrictions

Redemption Notice Period

(expressed in thousands)

Fidelity Growth Company Commingled Fund

725,056

—

Daily

None

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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Tabular disclosure of fair value of investment held by employee stock purchase, saving, or similar plan (employee benefit plan (EBP)), including, but not limited to, fair value measured at net asset value per share as practical expedient (NAV).

INVESTMENT IN AECOM DC RETIREMENT PLANS VANGUARD MASTER TRUST (Tables)

12 Months Ended

Dec. 31, 2025

Schedule of Net Assets of the Stable Value Master Trust

The following table presents the net assets of the Vanguard Master Trust as of December 31:


	Vanguard Master Trust
	2025		2024
	(expressed in thousands)
Investments at fair value
Collective investment trusts (measured at NAV)	$	3,413,123	$	2,734,006
Mutual funds	—		630,038

Net assets of Vanguard Master Trust	$	3,413,123	$	3,364,044

The following table shows the changes in net assets for the Vanguard Master Trust for the year ended December 31:


	2025
	(expressed in thousands)
Change in net assets:
Net appreciation in fair value of investments	$	532,759
Interest and dividend income	4
Total investment income	532,763

Net purchases (redemptions)	(482,636)
Administrative expenses	(1,048)

Net increase in net assets	49,079



Net assets:
Beginning of year	3,364,044
End of year	$	3,413,123


	As of December 31, 2024
	Quoted Prices in Active Markets for Identical Assets (Level 1)		Significant Observable Inputs (Level 2)		Total Fair Value
	(expressed in thousands)
Mutual funds	$	630,038	$	—	$	630,038
Total investments in the fair value hierarchy	$	630,038	$	—	$	630,038

Investments measured at NAV					2,734,006
Total investments at fair value					$	3,364,044

Net Asset Value per Share — The following tables summarize investments measured at NAV per share as of December 31, 2025 and 2024, respectively:

December 31, 2025

Fair Value

Unfunded Commitment

Redemption Frequency (if Currently Eligible)

Other Redemption Restrictions

Redemption Notice Period

(expressed in thousands)

Retirement date funds

2,016,233

—

Daily

None

Index funds

1,396,890

—

Daily

None

December 31, 2024

Fair Value

Unfunded Commitment

Redemption Frequency (if Currently Eligible)

Other Redemption Restrictions

Redemption Notice Period

(expressed in thousands)

Retirement date funds

1,503,727

—

Daily

None

Index funds

1,230,279

—

Daily

None

The following table presents the net assets of the SMA Master Trust as of December 31:


	SMA Master Trust
	2025		2024
	(expressed in thousands)
Investments at fair value
Stocks	$	—	$	269,919
Government bonds	68,339		48,545
Corporate bonds	86,656		74,084
Mortgage-backed securities	58,570		53,807
Asset-backed securities	6,733		6,144
Collective investment trusts	401,232		257,107
Cash and cash equivalents	4,822		8,610
	626,352		718,216
Accounts receivable
Receivable for securities sold	328		596
Accrued income	1,764		1,631
Other	515		514
	2,607		2,741
Accounts payable
Due to broker for securities purchased	(3,759)		(2,538)
Operating payables	(143)		(768)
	(3,902)		(3,306)

Net assets of SMA Master Trust	$	625,057	$	717,651

The following table shows the changes in net assets for the SMA Master Trust for the year ended December 31:


	2025
	(expressed in thousands)
Change in net assets:
Net appreciation in fair value of investments and income	$	150,726

Net purchases (redemptions)	(243,199)
Administrative expenses	(121)

Net decrease in net assets	(92,594)



Net assets:
Beginning of year	717,651
End of year	$	625,057

The following tables set forth by level, within the fair value hierarchy, the SMA Master Trust assets at fair value as of December 31, 2025 and 2024:


	As of December 31, 2025
	Quoted Prices in Active Markets for Identical Assets (Level 1)		Significant Observable Inputs (Level 2)		Total Fair Value
	(expressed in thousands)
Fixed income instruments:
Asset-backed securities	$	—	$	6,733	$	6,733
Mortgage-backed securities	—		58,570		58,570
Corporate bonds	—		86,656		86,656
Government bonds	—		68,339		68,339
Stocks	—		—		—
Cash and cash equivalents	4,822		—		4,822
Total investments at fair value	$	4,822	$	220,298	225,120

Investments measured at NAV					401,232
Total investments at fair value					$	626,352


	As of December 31, 2024
	Quoted Prices in Active Markets for Identical Assets (Level 1)		Significant Observable Inputs (Level 2)		Total Fair Value
	(expressed in thousands)
Fixed income instruments:
Asset-backed securities	$	—	$	6,144	$	6,144
Mortgage-backed securities	—		53,807		53,807
Corporate bonds	—		74,084		74,084
Government bonds	—		48,545		48,545
Stocks	269,919		—		269,919
Cash and cash equivalents	8,610		—		8,610
Total investments at fair value	$	278,529	$	182,580	461,109

Investments measured at NAV					257,107
Total investments at fair value					$	718,216

Net Asset Value per Share — The following table summarizes investments measured at NAV per share as of December 31, 2025 and 2024:

December 31, 2025

Fair Value

Unfunded Commitment

Redemption Frequency (if Currently Eligible)

Other Redemption Restrictions

Redemption Notice Period

(expressed in thousands)

Arrowstreet International Equity Fund

383,294

—

Daily

None

Northern Trust All Country World ex-U.S. Index Fund

17,938

—

Daily

None

December 31, 2024

Fair Value

Unfunded Commitment

Redemption Frequency (if Currently Eligible)

Other Redemption Restrictions

Redemption Notice Period

(expressed in thousands)

Arrowstreet International Equity Fund

253,548

—

Daily

None

Northern Trust All Country World ex-U.S. Index Fund

3,559

—

Daily

None

The following table presents the net assets of the Stable Value Master Trust as of December 31:


	Stable Value Master Trust
	2025		2024
	(expressed in thousands)
Investments measured at NAV
Collective investment trust	$	313,784	$	323,734

Net assets of Stable Value Master Trust	$	313,784	$	323,734

The following table shows the changes in net assets for the Stable Value Master Trust for the year ended December 31:


	2025
	(expressed in thousands)
Change in net assets:
Interest and dividend income	$	9,273

Net purchases (redemptions)	(19,214)
Administrative expenses	(9)

Net decrease in net assets	(9,950)



Net assets:
Beginning of year	323,734
End of year	$	313,784

Net Asset Value per Share — The following table summarizes investments measured at NAV per share as of December 31, 2025 and 2024:

December 31, 2025

Fair Value

Unfunded Commitment

Redemption Frequency (if Currently Eligible)

Other Redemption Restrictions

Redemption Notice Period

(expressed in thousands)

Stable value fund

313,784

—

Daily

None

December 31, 2024

Fair Value

Unfunded Commitment

Redemption Frequency (if Currently Eligible)

Other Redemption Restrictions

Redemption Notice Period

(expressed in thousands)

Stable value fund

323,734

—

Daily

None

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

Tabular disclosure of master trust arrangement in which employee stock purchase, saving, or similar plan (employee benefit plan (EBP)) participates.

+ References + Details

INVESTMENT IN AECOM DC RETIREMENT PLANS SMA MASTER TRUST (Details) - EBP 055 $ in Thousands	12 Months Ended
	Dec. 31, 2025 USD ($)
EBP, Change in Net Asset Available for Benefit, Increase (Decrease) from Income (Loss) on Investment [Abstract]
Net appreciation in fair value of investments and income	$ (48,300)
Net investment income	1,000,371
Beginning of year	6,778,558
End of year	7,368,267
Master Trust \| SMA Master Trust
EBP, Change in Net Asset Available for Benefit, Increase (Decrease) from Income (Loss) on Investment [Abstract]
Net appreciation in fair value of investments and income	150,726
Total investment income	(243,199)
Administrative expenses	(121)
Net investment income	(92,594)
Beginning of year	717,651
End of year	625,057
Plan interest in Master Trust \| SMA Master Trust
EBP, Change in Net Asset Available for Benefit, Increase (Decrease) from Income (Loss) on Investment [Abstract]
Net appreciation in fair value of investments and income	150,726
Total investment income	(243,199)
Administrative expenses	(121)
Net investment income	(92,594)
Beginning of year	717,651
End of year	$ 625,057

STATEMENT OF NET ASSETS AVAILABLE FOR BENEFITS - EBP 055 - USD ($) $ in Thousands	Dec. 31, 2025	Dec. 31, 2024
ASSETS:
Investments—at fair value (Notes B and C)	$ 2,939,566	$ 2,299,530
Total investments	7,291,530	6,704,959
Receivables
Notes receivable from participants (Notes A and B)	23,208	23,764
Employer contributions	53,095	49,565
Other	668	561
Total receivables	76,971	73,890
Total assets	7,368,501	6,778,849
LIABILITIES:
Accrued expenses	71	223
Payable to participants	163	68
Total liabilities	234	291
Net Assets Available for Benefits	7,368,267	6,778,558
Vanguard Master Trust (Note D)
ASSETS:
Plan investments in AECOM DC Retirement Plans (Note B):	3,413,123	3,364,044
SMA Master Trust (Note E)
ASSETS:
Plan investments in AECOM DC Retirement Plans (Note B):	625,057	717,651
Stable Value Master Trust (Note F)
ASSETS:
Plan investments in AECOM DC Retirement Plans (Note B):	$ 313,784	$ 323,734

DESCRIPTION OF THE PLAN

12 Months Ended

Dec. 31, 2025

EBP, Description of Plan [Line Items]

DESCRIPTION OF THE PLAN


A.			DESCRIPTION OF THE PLAN

The following brief description of the AECOM Retirement & Savings Plan (the “Plan”) is provided for general information purposes only. Participants should refer to the Plan document and the Summary Plan Description for more complete information.

General — The Plan is a defined contribution plan with a profit sharing component intended to qualify under Section 401(a) of the Internal Revenue Code (the "Code"), a cash or deferred arrangement intended to qualify under Sections 401(a) and 401(k) of the Code, and a non-leveraged employee stock ownership component intended to qualify under Sections 401(a), 409 and 4975(e)(7) of the Code, which is designed to invest primarily in shares of stock of the Company. It was established to provide benefits to eligible employees of AECOM (“AECOM” or the “Company”) and various participating affiliates. The Plan is administered by the AECOM Americas Benefits Administration Committee as authorized by AECOM. The Plan is subject to the applicable provisions of the Employee Retirement Income Security Act of 1974 (“ERISA”), as amended.

Merrill, Lynch, Pierce, Fenner & Smith, Inc. serves as the recordkeeper of the Plan. Assets of the Plan are held by Bank of America, N.A., the trustee (the “Trustee”), except for certain investments. Assets in the separately managed accounts are held by Northern Trust Corporation; the Vanguard investment funds are held by The Vanguard Group; and the stable value fund is held at Fidelity Management Trust Company on behalf of the Trustee.

Each participant is entitled to exercise voting rights attributable to the Company shares allocated to his or her account and is notified by the Trustee prior to the time that such rights are to be exercised. The Trustee votes for shares for which instructions have not been given by a participant in accordance with the trust agreement.

Eligibility — Eligible employees become eligible to participate in the Plan on their date of hire, and can enroll as soon as administratively feasible thereafter (“Eligible Employees,” as defined in the Plan document). If the Eligible Employee decides not to participate when they are first eligible, they may begin participating anytime, provided they are an Eligible Employee of the Company on that date.

Participant Contributions — Participants may voluntarily make pre-tax, Roth 401(k) and/or after-tax contributions in any combination. Pre-tax and Roth 401(k) contributions are limited to $23,500 for the calendar year 2025 per the Internal Revenue Service (“IRS”) limits. Contributions can be made in whole percentage increments up to 75 percent of eligible compensation, as defined in the Plan document. Participants who are 50 years of age and over may voluntarily make additional contributions on a pre-tax or to the extent permitted by applicable law, Roth 401(k) basis up to $7,500 for calendar year 2025 per IRS limits, which are counted as part of the Plan’s 75 percent limitation. If participants attain age 60 to 63 before the end of the 2025 calendar year, their total combined pre-tax catch-up contributions and Roth catch-up contributions may equal up to $11,250 for the 2025 calendar year. Participants also may contribute amounts representing rollovers from individual retirement accounts and/or other qualified plans. If participants are highly-compensated employees, the maximum contribution percentage may be subject to further limitation.

The Plan provides for an automatic enrollment feature for Eligible Employees. A participant’s contribution under the automatic enrollment feature will be a pre-tax contribution equal to one percent of his or her eligible compensation until either a participant elects to discontinue or change his or her election.

Participant Accounts — Each participant’s account is credited with the participant’s contributions and rollovers, Company contributions, and allocations of Plan investment earnings or losses. Allocations are based on participant earnings or account balances, as defined by the Plan document. Certain administration fees are paid from the participant’s account. The benefit to which a participant is entitled is the benefit that may be provided from the participant’s vested account.

Employer Contributions — The participants’ pre-tax and Roth 401(k) contributions made to the Plan are matched 50% by the Company up to 6% of eligible compensation. Participants’ after-tax contributions are not eligible for the

Company match. The Company’s annual match is allocated 50% to the participant’s selected investment allocations and 50% to AECOM common stock. Participants can transfer their account balance invested in AECOM common stock to other investment options and make withdrawals, subject to certain Plan and legal restrictions. In order to receive the annual match, participants must generally be employed on the last day of the Plan year. Notwithstanding the foregoing, participants covered by a collective bargaining agreement ("CBA"), government contract, or specific project agreement are eligible for a Company match (if any) as described in the applicable CBA, government contract, or specific project agreement.

Vesting — Participants’ contributions and rollovers, and the earnings thereon, are at all times vested in such participants’ accounts. Vesting in the Company contributions and associated earnings is based on years of continuous service. A participant vests in the Company contributions and associated earnings over a three-year period (33% after one year of service, 67% after two years of service, and 100% after three years of service). In addition, participants who are employees become fully vested upon attaining age 65, becoming disabled or deceased while employed at the Company, or upon termination of the Plan. Notwithstanding the foregoing, different vesting requirements may apply to (i) participants covered by a CBA, government contract, or specific project agreement, or (ii) participants acquired or terminated in connection with a corporate transaction.

The portion of a participant’s account balance that is not vested upon termination of employment is forfeited at the time the participant receives a distribution or as of the end of the Plan year in which the participant incurs five consecutive One-Year Breaks in Service, as defined in the Plan document, whichever occurs first. These unvested forfeited Company contributions and associated earnings are accumulated in the forfeiture account and are available to reduce subsequent Company contributions.

During the year ended December 31, 2025, forfeitures of approximately $1.2 million were used to offset the Company match for 2025. As of December 31, 2025 and 2024, the balance in the forfeiture account was $0.0 million and $0.0 million, respectively.

Investment Options — Upon enrollment in the Plan, a participant is allowed to direct the investment of his or her account into a variety of diversified investment funds offered by the Plan. If a participant is automatically enrolled in the Plan or otherwise has not selected an investment to invest his or her contributions to the Plan, those contributions are invested in a target date fund, as determined by the AECOM Americas Retirement Plan Investment Committee. Participants may change their selection of investments at any time.

One of the investment options offered under the Plan consists of shares of AECOM common stock, which is an employee stock ownership plan as defined in Section 4975(e)(7) of the Code within the Plan. In December 2021, AECOM initiated a dividend program on its shares of common stock. As a stockholder of AECOM common stock through the AECOM common stock fund, the Plan will receive dividends. The Plan will allocate the dividends to accounts of participants, which hold shares of AECOM common stock within the AECOM common stock fund, as of the dividend record date. The dividend will be deposited in the AECOM common stock fund unless the participant elects to receive it in cash outside of the Plan. Dividends deposited into the AECOM common stock fund account are reinvested to purchase more shares of AECOM common stock, which can be held or diversified into other investment funds in the Plan. The declaration and payment of dividends are subject to the sole discretion of the Company’s board of directors.

Notes Receivable from Participants — Active participants may obtain loans from their vested account balances provided they meet the Plan’s eligibility requirements. The minimum loan amount permitted is $1,000; the maximum is the lesser of $50,000 or 50% of the participant’s vested account balance. The interest rates are no less than 1% over the prime rate as published in The Wall Street Journal, in effect on the first business day of the month in which the loan application is made. Notes receivable from participants bear interest at rates that range from 4.25% to 9.50% at December 31, 2025 and 2024. The repayment period of such loans cannot exceed five years, unless the proceeds are used to buy the participant’s principal residence, in which case longer terms, up to twenty years, are allowed. These loans are secured by a promissory note from the participant and his or her vested interest in the Plan.

Distributions — Generally, distributions are made upon a participant’s election after a participant terminates employment, becomes disabled, dies, or turns age 59-1/2 (in the event of death, payment shall be made to his or her beneficiary or, if none, to his or her surviving spouse, civil union partner, or state-registered domestic partner or, if

none, to his or her legal representatives in care of his or her estate). A partial or complete distribution may be made in a lump-sum in the form of cash or in-kind distribution (in case of Company shares). Distributions may also be made in monthly, quarterly, semi-annual, or annual installments, or in a direct rollover distribution. Distribution options for members of certain acquired companies, provided in previously merged plans, were grandfathered in as a protected benefit. In addition, withdrawals of specific contributions or coverage of certain qualified expenses resulting from an emergency, disaster, hardship, or the birth or adoption of a child may be permitted from vested amounts during employment.

INVESTMENT IN AECOM DC RETIREMENT PLANS STABLE VALUE MASTER TRUST (Tables)

12 Months Ended

Dec. 31, 2025

Schedule of Net Assets of the Stable Value Master Trust

The following table presents the net assets of the Vanguard Master Trust as of December 31:


	Vanguard Master Trust
	2025		2024
	(expressed in thousands)
Investments at fair value
Collective investment trusts (measured at NAV)	$	3,413,123	$	2,734,006
Mutual funds	—		630,038

Net assets of Vanguard Master Trust	$	3,413,123	$	3,364,044

The following table shows the changes in net assets for the Vanguard Master Trust for the year ended December 31:


	2025
	(expressed in thousands)
Change in net assets:
Net appreciation in fair value of investments	$	532,759
Interest and dividend income	4
Total investment income	532,763

Net purchases (redemptions)	(482,636)
Administrative expenses	(1,048)

Net increase in net assets	49,079



Net assets:
Beginning of year	3,364,044
End of year	$	3,413,123


	As of December 31, 2024
	Quoted Prices in Active Markets for Identical Assets (Level 1)		Significant Observable Inputs (Level 2)		Total Fair Value
	(expressed in thousands)
Mutual funds	$	630,038	$	—	$	630,038
Total investments in the fair value hierarchy	$	630,038	$	—	$	630,038

Investments measured at NAV					2,734,006
Total investments at fair value					$	3,364,044

Net Asset Value per Share — The following tables summarize investments measured at NAV per share as of December 31, 2025 and 2024, respectively:

December 31, 2025

Fair Value

Unfunded Commitment

Redemption Frequency (if Currently Eligible)

Other Redemption Restrictions

Redemption Notice Period

(expressed in thousands)

Retirement date funds

2,016,233

—

Daily

None

Index funds

1,396,890

—

Daily

None

December 31, 2024

Fair Value

Unfunded Commitment

Redemption Frequency (if Currently Eligible)

Other Redemption Restrictions

Redemption Notice Period

(expressed in thousands)

Retirement date funds

1,503,727

—

Daily

None

Index funds

1,230,279

—

Daily

None

The following table presents the net assets of the SMA Master Trust as of December 31:


	SMA Master Trust
	2025		2024
	(expressed in thousands)
Investments at fair value
Stocks	$	—	$	269,919
Government bonds	68,339		48,545
Corporate bonds	86,656		74,084
Mortgage-backed securities	58,570		53,807
Asset-backed securities	6,733		6,144
Collective investment trusts	401,232		257,107
Cash and cash equivalents	4,822		8,610
	626,352		718,216
Accounts receivable
Receivable for securities sold	328		596
Accrued income	1,764		1,631
Other	515		514
	2,607		2,741
Accounts payable
Due to broker for securities purchased	(3,759)		(2,538)
Operating payables	(143)		(768)
	(3,902)		(3,306)

Net assets of SMA Master Trust	$	625,057	$	717,651

The following table shows the changes in net assets for the SMA Master Trust for the year ended December 31:


	2025
	(expressed in thousands)
Change in net assets:
Net appreciation in fair value of investments and income	$	150,726

Net purchases (redemptions)	(243,199)
Administrative expenses	(121)

Net decrease in net assets	(92,594)



Net assets:
Beginning of year	717,651
End of year	$	625,057

The following tables set forth by level, within the fair value hierarchy, the SMA Master Trust assets at fair value as of December 31, 2025 and 2024:


	As of December 31, 2025
	Quoted Prices in Active Markets for Identical Assets (Level 1)		Significant Observable Inputs (Level 2)		Total Fair Value
	(expressed in thousands)
Fixed income instruments:
Asset-backed securities	$	—	$	6,733	$	6,733
Mortgage-backed securities	—		58,570		58,570
Corporate bonds	—		86,656		86,656
Government bonds	—		68,339		68,339
Stocks	—		—		—
Cash and cash equivalents	4,822		—		4,822
Total investments at fair value	$	4,822	$	220,298	225,120

Investments measured at NAV					401,232
Total investments at fair value					$	626,352


	As of December 31, 2024
	Quoted Prices in Active Markets for Identical Assets (Level 1)		Significant Observable Inputs (Level 2)		Total Fair Value
	(expressed in thousands)
Fixed income instruments:
Asset-backed securities	$	—	$	6,144	$	6,144
Mortgage-backed securities	—		53,807		53,807
Corporate bonds	—		74,084		74,084
Government bonds	—		48,545		48,545
Stocks	269,919		—		269,919
Cash and cash equivalents	8,610		—		8,610
Total investments at fair value	$	278,529	$	182,580	461,109

Investments measured at NAV					257,107
Total investments at fair value					$	718,216

Net Asset Value per Share — The following table summarizes investments measured at NAV per share as of December 31, 2025 and 2024:

December 31, 2025

Fair Value

Unfunded Commitment

Redemption Frequency (if Currently Eligible)

Other Redemption Restrictions

Redemption Notice Period

(expressed in thousands)

Arrowstreet International Equity Fund

383,294

—

Daily

None

Northern Trust All Country World ex-U.S. Index Fund

17,938

—

Daily

None

December 31, 2024

Fair Value

Unfunded Commitment

Redemption Frequency (if Currently Eligible)

Other Redemption Restrictions

Redemption Notice Period

(expressed in thousands)

Arrowstreet International Equity Fund

253,548

—

Daily

None

Northern Trust All Country World ex-U.S. Index Fund

3,559

—

Daily

None

The following table presents the net assets of the Stable Value Master Trust as of December 31:


	Stable Value Master Trust
	2025		2024
	(expressed in thousands)
Investments measured at NAV
Collective investment trust	$	313,784	$	323,734

Net assets of Stable Value Master Trust	$	313,784	$	323,734

The following table shows the changes in net assets for the Stable Value Master Trust for the year ended December 31:


	2025
	(expressed in thousands)
Change in net assets:
Interest and dividend income	$	9,273

Net purchases (redemptions)	(19,214)
Administrative expenses	(9)

Net decrease in net assets	(9,950)



Net assets:
Beginning of year	323,734
End of year	$	313,784

Net Asset Value per Share — The following table summarizes investments measured at NAV per share as of December 31, 2025 and 2024:

December 31, 2025

Fair Value

Unfunded Commitment

Redemption Frequency (if Currently Eligible)

Other Redemption Restrictions

Redemption Notice Period

(expressed in thousands)

Stable value fund

313,784

—

Daily

None

December 31, 2024

Fair Value

Unfunded Commitment

Redemption Frequency (if Currently Eligible)

Other Redemption Restrictions

Redemption Notice Period

(expressed in thousands)

Stable value fund

323,734

—

Daily

None

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

Tabular disclosure of master trust arrangement in which employee stock purchase, saving, or similar plan (employee benefit plan (EBP)) participates.

+ References + Details

RELATED PARTY TRANSACTIONS (Details) - EBP 055 - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2025	Dec. 31, 2024
EBP, Related Party and Party-in-Interest Transactions [Line Items]
Total investments at fair value	$ 2,939,566	$ 2,299,530
Dividend income recorded	5,100
Net depreciation in fair value of shares bought and sold, as well as held during the year	48,300
Delinquent deposits of employee deferrals and loan repayments	$ 17,000	$ 8,000
AECOM common stock
EBP, Related Party and Party-in-Interest Transactions [Line Items]
Plan investments held (in shares)	4,686,516	4,900,000
Total investments at fair value	$ 446,500	$ 521,700
Investments acquired during the period	59,800
AECOM common stock issued by the Company to the Plan	26,000
Investments sold during the period	91,700
In-kind distributions	$ 20,400

INVESTMENT IN AECOM DC RETIREMENT PLANS VANGUARD MASTER TRUST

12 Months Ended

Dec. 31, 2025

INVESTMENT IN AECOM DC RETIREMENT PLANS VANGUARD MASTER TRUST


D.			INVESTMENT IN AECOM DC RETIREMENT PLANS VANGUARD MASTER TRUST

The following table presents the net assets of the Vanguard Master Trust as of December 31:


	Vanguard Master Trust
	2025		2024
	(expressed in thousands)
Investments at fair value
Collective investment trusts (measured at NAV)	$	3,413,123	$	2,734,006
Mutual funds	—		630,038

Net assets of Vanguard Master Trust	$	3,413,123	$	3,364,044

The following table shows the changes in net assets for the Vanguard Master Trust for the year ended December 31:


	2025
	(expressed in thousands)
Change in net assets:
Net appreciation in fair value of investments	$	532,759
Interest and dividend income	4
Total investment income	532,763

Net purchases (redemptions)	(482,636)
Administrative expenses	(1,048)

Net increase in net assets	49,079



Net assets:
Beginning of year	3,364,044
End of year	$	3,413,123


	As of December 31, 2024
	Quoted Prices in Active Markets for Identical Assets (Level 1)		Significant Observable Inputs (Level 2)		Total Fair Value
	(expressed in thousands)
Mutual funds	$	630,038	$	—	$	630,038
Total investments in the fair value hierarchy	$	630,038	$	—	$	630,038

Investments measured at NAV					2,734,006
Total investments at fair value					$	3,364,044

Net Asset Value per Share — The following tables summarize investments measured at NAV per share as of December 31, 2025 and 2024, respectively:

December 31, 2025

Fair Value

Unfunded Commitment

Redemption Frequency (if Currently Eligible)

Other Redemption Restrictions

Redemption Notice Period

(expressed in thousands)

Retirement date funds

2,016,233

—

Daily

None

Index funds

1,396,890

—

Daily

None

December 31, 2024

Fair Value

Unfunded Commitment

Redemption Frequency (if Currently Eligible)

Other Redemption Restrictions

Redemption Notice Period

(expressed in thousands)

Retirement date funds

1,503,727

—

Daily

None

Index funds

1,230,279

—

Daily

None


E.			INVESTMENT IN AECOM DC RETIREMENT PLANS SMA MASTER TRUST

The following table presents the net assets of the SMA Master Trust as of December 31:


	SMA Master Trust
	2025		2024
	(expressed in thousands)
Investments at fair value
Stocks	$	—	$	269,919
Government bonds	68,339		48,545
Corporate bonds	86,656		74,084
Mortgage-backed securities	58,570		53,807
Asset-backed securities	6,733		6,144
Collective investment trusts	401,232		257,107
Cash and cash equivalents	4,822		8,610
	626,352		718,216
Accounts receivable
Receivable for securities sold	328		596
Accrued income	1,764		1,631
Other	515		514
	2,607		2,741
Accounts payable
Due to broker for securities purchased	(3,759)		(2,538)
Operating payables	(143)		(768)
	(3,902)		(3,306)

Net assets of SMA Master Trust	$	625,057	$	717,651

The following table shows the changes in net assets for the SMA Master Trust for the year ended December 31:


	2025
	(expressed in thousands)
Change in net assets:
Net appreciation in fair value of investments and income	$	150,726

Net purchases (redemptions)	(243,199)
Administrative expenses	(121)

Net decrease in net assets	(92,594)



Net assets:
Beginning of year	717,651
End of year	$	625,057

The following tables set forth by level, within the fair value hierarchy, the SMA Master Trust assets at fair value as of December 31, 2025 and 2024:


	As of December 31, 2025
	Quoted Prices in Active Markets for Identical Assets (Level 1)		Significant Observable Inputs (Level 2)		Total Fair Value
	(expressed in thousands)
Fixed income instruments:
Asset-backed securities	$	—	$	6,733	$	6,733
Mortgage-backed securities	—		58,570		58,570
Corporate bonds	—		86,656		86,656
Government bonds	—		68,339		68,339
Stocks	—		—		—
Cash and cash equivalents	4,822		—		4,822
Total investments at fair value	$	4,822	$	220,298	225,120

Investments measured at NAV					401,232
Total investments at fair value					$	626,352


	As of December 31, 2024
	Quoted Prices in Active Markets for Identical Assets (Level 1)		Significant Observable Inputs (Level 2)		Total Fair Value
	(expressed in thousands)
Fixed income instruments:
Asset-backed securities	$	—	$	6,144	$	6,144
Mortgage-backed securities	—		53,807		53,807
Corporate bonds	—		74,084		74,084
Government bonds	—		48,545		48,545
Stocks	269,919		—		269,919
Cash and cash equivalents	8,610		—		8,610
Total investments at fair value	$	278,529	$	182,580	461,109

Investments measured at NAV					257,107
Total investments at fair value					$	718,216

Net Asset Value per Share — The following table summarizes investments measured at NAV per share as of December 31, 2025 and 2024:

December 31, 2025

Fair Value

Unfunded Commitment

Redemption Frequency (if Currently Eligible)

Other Redemption Restrictions

Redemption Notice Period

(expressed in thousands)

Arrowstreet International Equity Fund

383,294

—

Daily

None

Northern Trust All Country World ex-U.S. Index Fund

17,938

—

Daily

None

December 31, 2024

Fair Value

Unfunded Commitment

Redemption Frequency (if Currently Eligible)

Other Redemption Restrictions

Redemption Notice Period

(expressed in thousands)

Arrowstreet International Equity Fund

253,548

—

Daily

None

Northern Trust All Country World ex-U.S. Index Fund

3,559

—

Daily

None


F.			INVESTMENT IN AECOM DC RETIREMENT PLANS STABLE VALUE MASTER TRUST

The following table presents the net assets of the Stable Value Master Trust as of December 31:


	Stable Value Master Trust
	2025		2024
	(expressed in thousands)
Investments measured at NAV
Collective investment trust	$	313,784	$	323,734

Net assets of Stable Value Master Trust	$	313,784	$	323,734

The following table shows the changes in net assets for the Stable Value Master Trust for the year ended December 31:


	2025
	(expressed in thousands)
Change in net assets:
Interest and dividend income	$	9,273

Net purchases (redemptions)	(19,214)
Administrative expenses	(9)

Net decrease in net assets	(9,950)



Net assets:
Beginning of year	323,734
End of year	$	313,784

Net Asset Value per Share — The following table summarizes investments measured at NAV per share as of December 31, 2025 and 2024:

December 31, 2025

Fair Value

Unfunded Commitment

Redemption Frequency (if Currently Eligible)

Other Redemption Restrictions

Redemption Notice Period

(expressed in thousands)

Stable value fund

313,784

—

Daily

None

December 31, 2024

Fair Value

Unfunded Commitment

Redemption Frequency (if Currently Eligible)

Other Redemption Restrictions

Redemption Notice Period

(expressed in thousands)

Stable value fund

323,734

—

Daily

None

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

The entire disclosure for master trust arrangement in which employee stock purchase, saving, or similar plan (employee benefit plan (EBP)) participates.

FAIR VALUE MEASUREMENTS

12 Months Ended

Dec. 31, 2025

EBP, Investment, Fair Value and NAV [Line Items]

FAIR VALUE MEASUREMENTS


C.			FAIR VALUE MEASUREMENTS

Below are the Plan’s investments carried at fair value on a recurring basis by the ASC 820-10 fair value hierarchy levels described in Note B:


	As of December 31, 2025
	Quoted Prices in Active Markets for Identical Assets (Level 1)		Significant Observable Inputs (Level 2)		Total Fair Value
	(expressed in thousands)
Mutual funds	$	573,112	$	—	$	573,112
AECOM common stock	446,480		—		446,480
Self-directed brokerage accounts	495,278		24,468		519,746
Total investments in the fair value hierarchy	$	1,514,870	$	24,468	$	1,539,338
Investments measured at NAV					1,400,228
Total investments at fair value					$	2,939,566


	As of December 31, 2024
	Quoted Prices in Active Markets for Identical Assets (Level 1)		Significant Observable Inputs (Level 2)		Total Fair Value
	(expressed in thousands)
Mutual funds	$	597,766	$	—	$	597,766
AECOM common stock	521,670		—		521,670
Self-directed brokerage accounts	430,682		24,356		455,038
Total investments in the fair value hierarchy	$	1,550,118	$	24,356	$	1,574,474
Investments measured at NAV					725,056
Total investments at fair value					$	2,299,530

Net Asset Value per Share — The following tables summarize investments measured at NAV per share as of December 31, 2025 and 2024:

December 31, 2025

Fair Value

Unfunded Commitment

Redemption Frequency (if Currently Eligible)

Other Redemption Restrictions

Redemption Notice Period

(expressed in thousands)

Fidelity Growth Company Commingled Fund

568,254

—

Daily

None

T. Rowe Price Structured Research Common Trust Fund

585,114

—

Daily

None

EARNEST Partners Emerging Market Fund

246,860

—

Daily

None

December 31, 2024

Fair Value

Unfunded Commitment

Redemption Frequency (if Currently Eligible)

Other Redemption Restrictions

Redemption Notice Period

(expressed in thousands)

Fidelity Growth Company Commingled Fund

725,056

—

Daily

None

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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The entire disclosure for fair value of investment held by employee stock purchase, saving, or similar plan (employee benefit plan (EBP)), including, but not limited to, fair value measured at net asset value per share as practical expedient (NAV).

Investment Valuation and Income Recognition

STATEMENT OF CHANGES IN NET ASSETS AVAILABLE FOR BENEFITS - EBP 055 $ in Thousands	12 Months Ended
	Dec. 31, 2025 USD ($)
INVESTMENT INCOME:
Net appreciation in fair value of investments and Investment gain from self-directed brokerage accounts	$ 221,593
Interest and dividends	7,184
Investment gain from self-directed brokerage accounts	78,832
Net investment income	1,000,371
INTEREST INCOME ON NOTES RECEIVABLE FROM PARTICIPANTS	1,783
CONTRIBUTIONS:
Participants	222,124
Employer	53,448
Total contributions	275,572
Total additions	1,277,726
DEDUCTIONS FROM NET ASSETS ATTRIBUTED TO:
Benefits paid to participants (Note A and Note G)	(686,681)
Administrative expenses	(1,336)
Total deductions	(688,017)
NET INCREASE	589,709
Beginning of year	6,778,558
End of year	7,368,267
Vanguard Master Trust (Note D)
INVESTMENT INCOME:
Plan interest in the investment income of the AECOM DC Retirement Plans:	532,763
SMA Master Trust (Note E)
INVESTMENT INCOME:
Plan interest in the investment income of the AECOM DC Retirement Plans:	150,726
Stable Value Master Trust (Note F)
INVESTMENT INCOME:
Plan interest in the investment income of the AECOM DC Retirement Plans:	$ 9,273

INVESTMENT IN AECOM DC RETIREMENT PLANS VANGUARD MASTER TRUST (Details) - EBP 055 - USD ($) $ in Thousands	Dec. 31, 2025	Dec. 31, 2024
EBP, Master Trust [Line Items]
Investments at fair value	$ 7,291,530	$ 6,704,959
Vanguard Master Trust
EBP, Master Trust [Line Items]
Plan's interest in Master Trust (percent)	100.00%
Master Trust \| Vanguard Master Trust
EBP, Master Trust [Line Items]
Investments at fair value	$ 3,413,123	3,364,044
Master Trust \| Vanguard Master Trust \| Total Fair Value
EBP, Master Trust [Line Items]
Investments at fair value		630,038
Master Trust \| Vanguard Master Trust \| Level 1
EBP, Master Trust [Line Items]
Investments at fair value		630,038
Master Trust \| Vanguard Master Trust \| Level 2
EBP, Master Trust [Line Items]
Investments at fair value		0
Master Trust \| Vanguard Master Trust \| Collective investment trusts (measured at NAV)
EBP, Master Trust [Line Items]
Investments at fair value	3,413,123	2,734,006
Master Trust \| Vanguard Master Trust \| Collective investment trusts (measured at NAV) \| Investments measured at NAV
EBP, Master Trust [Line Items]
Investments at fair value		2,734,006
Master Trust \| Vanguard Master Trust \| Mutual funds
EBP, Master Trust [Line Items]
Investments at fair value	0	630,038
Master Trust \| Vanguard Master Trust \| Mutual funds \| Total Fair Value
EBP, Master Trust [Line Items]
Investments at fair value		630,038
Master Trust \| Vanguard Master Trust \| Mutual funds \| Level 1
EBP, Master Trust [Line Items]
Investments at fair value		630,038
Master Trust \| Vanguard Master Trust \| Mutual funds \| Level 2
EBP, Master Trust [Line Items]
Investments at fair value		0
Master Trust \| Vanguard Master Trust \| Retirement date funds
EBP, Master Trust [Line Items]
Investments at fair value	2,016,233	1,503,727
Unfunded Commitment	0	0
Master Trust \| Vanguard Master Trust \| Index funds
EBP, Master Trust [Line Items]
Investments at fair value	1,396,890	1,230,279
Unfunded Commitment	0	0
Plan interest in Master Trust \| Vanguard Master Trust
EBP, Master Trust [Line Items]
Investments at fair value	3,413,123	3,364,044
Plan interest in Master Trust \| Vanguard Master Trust \| Total Fair Value
EBP, Master Trust [Line Items]
Investments at fair value		630,038
Plan interest in Master Trust \| Vanguard Master Trust \| Level 1
EBP, Master Trust [Line Items]
Investments at fair value		630,038
Plan interest in Master Trust \| Vanguard Master Trust \| Level 2
EBP, Master Trust [Line Items]
Investments at fair value		0
Plan interest in Master Trust \| Vanguard Master Trust \| Collective investment trusts (measured at NAV)
EBP, Master Trust [Line Items]
Investments at fair value	3,413,123	2,734,006
Plan interest in Master Trust \| Vanguard Master Trust \| Collective investment trusts (measured at NAV) \| Investments measured at NAV
EBP, Master Trust [Line Items]
Investments at fair value		2,734,006
Plan interest in Master Trust \| Vanguard Master Trust \| Mutual funds
EBP, Master Trust [Line Items]
Investments at fair value	0	630,038
Plan interest in Master Trust \| Vanguard Master Trust \| Mutual funds \| Total Fair Value
EBP, Master Trust [Line Items]
Investments at fair value		630,038
Plan interest in Master Trust \| Vanguard Master Trust \| Mutual funds \| Level 1
EBP, Master Trust [Line Items]
Investments at fair value		630,038
Plan interest in Master Trust \| Vanguard Master Trust \| Mutual funds \| Level 2
EBP, Master Trust [Line Items]
Investments at fair value		0
Plan interest in Master Trust \| Vanguard Master Trust \| Retirement date funds
EBP, Master Trust [Line Items]
Investments at fair value	2,016,233	1,503,727
Unfunded Commitment	0	0
Plan interest in Master Trust \| Vanguard Master Trust \| Index funds
EBP, Master Trust [Line Items]
Investments at fair value	1,396,890	1,230,279
Unfunded Commitment	$ 0	$ 0

FAIR VALUE MEASUREMENTS - Fair Value of Investments (Details) - EBP 055 - USD ($) $ in Thousands	Dec. 31, 2025	Dec. 31, 2024
EBP, Investment, Fair Value and NAV [Line Items]
Total investments at fair value	$ 2,939,566	$ 2,299,530
AECOM common stock
EBP, Investment, Fair Value and NAV [Line Items]
Total investments at fair value	446,500	521,700
Total Fair Value
EBP, Investment, Fair Value and NAV [Line Items]
Total investments at fair value	1,539,338	1,574,474
Total Fair Value \| Mutual funds
EBP, Investment, Fair Value and NAV [Line Items]
Total investments at fair value	573,112	597,766
Total Fair Value \| AECOM common stock
EBP, Investment, Fair Value and NAV [Line Items]
Total investments at fair value	446,480	521,670
Total Fair Value \| Self-directed brokerage accounts
EBP, Investment, Fair Value and NAV [Line Items]
Total investments at fair value	519,746	455,038
Level 1
EBP, Investment, Fair Value and NAV [Line Items]
Total investments at fair value	1,514,870	1,550,118
Level 1 \| Mutual funds
EBP, Investment, Fair Value and NAV [Line Items]
Total investments at fair value	573,112	597,766
Level 1 \| AECOM common stock
EBP, Investment, Fair Value and NAV [Line Items]
Total investments at fair value	446,480	521,670
Level 1 \| Self-directed brokerage accounts
EBP, Investment, Fair Value and NAV [Line Items]
Total investments at fair value	495,278	430,682
Level 2
EBP, Investment, Fair Value and NAV [Line Items]
Total investments at fair value	24,468	24,356
Level 2 \| Mutual funds
EBP, Investment, Fair Value and NAV [Line Items]
Total investments at fair value	0	0
Level 2 \| AECOM common stock
EBP, Investment, Fair Value and NAV [Line Items]
Total investments at fair value	0	0
Level 2 \| Self-directed brokerage accounts
EBP, Investment, Fair Value and NAV [Line Items]
Total investments at fair value	24,468	24,356
Investments measured at NAV
EBP, Investment, Fair Value and NAV [Line Items]
Total investments at fair value	$ 1,400,228	$ 725,056

SIGNIFICANT ACCOUNTING POLICIES (Policies) - EBP 055

12 Months Ended

Dec. 31, 2025

EBP, Accounting Policy [Line Items]

Basis of Accounting

Basis of Accounting — The accompanying financial statements have been prepared on the accrual basis of accounting in accordance with accounting principles generally accepted in the United States of America.

Use of Estimates

Use of Estimates — The preparation of financial statements in conformity with accounting principles generally accepted in the United States of America requires the Plan’s management to make estimates and assumptions that affect certain reported amounts and disclosures. Accordingly, actual results could differ from those estimates.

Investment Valuation and Income Recognition — Investments held by the Plan are reported at fair value. Fair value is the price that would be received from selling an asset or paid to transfer a liability in an orderly transaction between market participants at the measurement date. The cost of investments sold or distributed is determined on the basis of the average cost for each participant. Purchases and sales of securities are reflected on the trade date. Transactions pending clearance with brokers not settled at year-end are recorded as other receivables or payables on the Statements of Net Assets Available for Benefits. Dividends are recorded on the ex-dividend date. Interest income is recorded as earned. Net appreciation or depreciation in fair value of investments includes the Plan’s gains and losses on investments bought and sold as well as held during the year.

Net investment income (loss) of the AECOM DC Retirement Plans Vanguard Master Trust, the AECOM DC Retirement Plans SMA Master Trust, and the AECOM DC Retirement Plans Stable Value Master Trust (collectively, the “Master Trusts”) is allocated daily to the Plan based on the ratio of the Plan’s investment in the Master Trusts to the total value of the related investments held by each master trust as of the beginning of the day.

Notes Receivable from Participants

Notes Receivable from Participants — Notes receivable from participants are measured at their principal balance plus any accrued interest. Interest income is recorded on the accrual basis. Related fees are recorded as administrative expenses and are expensed when they are incurred. No allowance for credit losses has been recorded as of December 31, 2025 or 2024. If a participant ceases to make loan repayments and the Plan administrator deems the participant loan to be in default, the participant loan balance is reduced, and a benefit payment is recorded.

Payment of Benefits

Payment of Benefits — Benefits are recorded when paid by the Plan.

Plan Expenses

Administrative Expenses — The Plan incurs monthly recordkeeping and administrative expenses. Specific participant transaction expenses are deducted from participant accounts directly. Plan expenses that cannot be directly charged to a specific participant transaction may be paid, in whole or in part, from a twelve-dollar quarterly administrative fee charged to participant accounts. For the year ended December 31, 2025, the Plan incurred $1.3 million of recordkeeping and administrative expenses.

Fair Value Measurements

Fair Value Measurements — The Plan’s investments, which are stated at fair value, are disclosed in accordance with the established framework and disclosure requirements described in the Financial Accounting Standards Board Accounting Standards Codification No. 820-10, “Fair Value Measurements and Disclosures” (“ASC 820-10”), which defines fair value, establishes a framework for measuring fair value under current accounting pronouncements that require or permit fair value measurement, and enhances disclosures about fair value measurements. ASC 820-10 defines fair value as the exchange price that would be received for an asset or paid to transfer a liability (an exit price) in the principal or most advantageous market for the asset or liability in an orderly transaction which requires an entity to maximize the use of observable inputs when measuring fair value.

The standard describes three levels of inputs that may be used to measure fair value:


			Level 1 —			Inputs to the valuation methodology are quoted prices available in active markets for identical investments as of the reporting date.
			Level 2 —			Inputs to the valuation methodology include:
						•quoted prices for similar assets or liabilities in active markets;
						•quoted prices for identical or similar assets or liabilities in inactive markets;
						•inputs other than quoted prices that are observable for the asset or liability;
						•inputs that are derived principally from or corroborated by observable market data by correlation or other means.
						If the asset or liability has a specified (contractual) term, the Level 2 input must be observable for substantially the full term of the asset or liability.
			Level 3 —			Inputs to the valuation methodology are unobservable inputs in situations where there is little or no market activity for the asset or liability and the reporting entity makes estimates and assumptions related to the pricing of the asset or liability including assumptions regarding risk.

A financial instrument’s level within the fair value hierarchy is based on the lowest level of any input that is significant to the fair value measurement.

The following is a description of the valuation methodologies used for instruments measured at fair value, including the general classification of such instruments pursuant to the valuation hierarchy.

Common Stock and Other Exchange-Traded Equity Securities Including AECOM Stock

The fair value of these instruments is based on the closing price per the principal stock exchange on which they are traded and are classified within Level 1 of the valuation hierarchy. AECOM common stock is valued at the closing price reported on the New York Stock Exchange Composite Listing and is classified within Level 1 of the valuation hierarchy.

Mutual Funds

A mutual fund is an investment company registered under the Investment Company Act of 1940 that pools the capital of many investors and invests it in stocks, bonds, short-term money market instruments, and/or other securities. These investments are public investment vehicles valued at the closing price reported in the active market in which the investments are traded. These investments are classified within Level 1 of the valuation hierarchy.

Self-Directed Brokerage Accounts

Self-directed brokerage accounts are comprised of investments which are valued at the closing price reported in the active market in which the investments are traded. These investments are classified within Level 1 of the valuation hierarchy. In addition, the self-directed brokerage accounts also hold investments in fixed income instruments, such as government and corporate bonds, and certificate of deposits. Accordingly, these investments are classified within Level 2 of the valuation hierarchy.

Fixed Income Instruments

Fixed income instruments are valued based on prices received from the fund custodian. The custodian uses multiple valuation techniques to determine the valuation of fixed income instruments. In instances where there is sufficient market activity, the custodian may utilize a market-based approach through which trades or quotes from similar instruments with comparable durations, yields, and credit ratings are used to determine the valuation of these instruments. In instances where there is insufficient market activity, the custodian may utilize proprietary valuation models that maximize observable inputs. The valuation models may consider market transactions in comparable securities, the various relationships between securities, and/or market characteristics to estimate the relevant cash flows, which are then discounted to calculate the fair values. Fixed income securities, which are valued based on significant observable inputs, are classified within Level 2 of the valuation hierarchy because quoted prices of identical instruments are not readily available in active markets.

Collective Investment Trusts

A collective investment trust is a trust for the collective investment and reinvestment of assets contributed from employee benefit plans maintained by more than one plan. These investments are valued using the net asset value (“NAV”) provided by the administrator of the collective trust. The NAV is based on the value of the underlying assets owned by the fund, minus its liabilities, and then divided by the number of shares outstanding. The NAV is used as a practical expedient to estimate fair value. The collective investment trusts are not classified within the fair value hierarchy; however, the amounts measured using NAV is disclosed to permit reconciliation of the fair value of investments to the Statements of Net Assets Available for Benefits. These funds may also include short-term investment funds, which are valued based on significant observable inputs, and are classified within Level 2 of the valuation hierarchy.

White Label Funds

The Plan has two white label funds, the AECOM U.S. Large Cap Stock Fund and the AECOM U.S. Small-Mid Cap Stock Fund. These funds are custom investment options that employ a fund of funds approach, where the fund's assets are diversified across multiple stock portfolios. The AECOM U.S. Large Cap Stock Fund currently consist of two collective investment trusts and a mutual fund that are designed to provide long-term capital growth, with performance benchmarked against the Russell 1000 Index. The AECOM U.S. Small-Mid Cap Stock Fund currently consist of a single investment in a collective investment trust that is designed to provide capital appreciation by investing primarily in U.S. common stocks of small- and mid-sized companies included in the Russell 2500 Index. The fair value of the white label funds are based on the underlying assets which are currently Level 1 of the valuation hierarchy and using the NAV as a practical expedient.

Subsequent Events

Subsequent Events — The Plan monitors significant events occurring after the balance sheet date and prior to the issuance of the financial statements to determine the impacts, if any, of events on the financial statements to be issued. The Plan has evaluated subsequent events through the date which the financial statements are issued.

FAIR VALUE MEASUREMENTS - Investments Measured at NAV per share (Details) - EBP 055 - USD ($) $ in Thousands	Dec. 31, 2025	Dec. 31, 2024
EBP, Investment, Fair Value and NAV [Line Items]
Total investments at fair value	$ 2,939,566	$ 2,299,530
Investments measured at NAV
EBP, Investment, Fair Value and NAV [Line Items]
Total investments at fair value	1,400,228	725,056
Investments measured at NAV \| Fidelity Growth Company Commingled Fund
EBP, Investment, Fair Value and NAV [Line Items]
Total investments at fair value	568,254	725,056
Unfunded Commitment	0	$ 0
Investments measured at NAV \| T. Rowe Price Structured Research Common Trust Fund
EBP, Investment, Fair Value and NAV [Line Items]
Total investments at fair value	585,114
Unfunded Commitment	0
Investments measured at NAV \| EARNEST Partners Emerging Market Fund
EBP, Investment, Fair Value and NAV [Line Items]
Total investments at fair value	246,860
Unfunded Commitment	$ 0

Fair value of investment, excluding plan interest in master trust, held by employee stock purchase, saving, or similar plan (employee benefit plan (EBP)). Includes, but is not limited to, derivative, investment measured at net asset value per share as practical expedient, and insurance contract not meeting fully-benefit responsive investment criteria.

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SIGNIFICANT ACCOUNTING POLICIES

12 Months Ended

Dec. 31, 2025

SIGNIFICANT ACCOUNTING POLICIES

EBP, Accounting Policy [Line Items]


B.			SIGNIFICANT ACCOUNTING POLICIES

Payment of Benefits — Benefits are recorded when paid by the Plan.

The standard describes three levels of inputs that may be used to measure fair value:


			Level 1 —			Inputs to the valuation methodology are quoted prices available in active markets for identical investments as of the reporting date.
			Level 2 —			Inputs to the valuation methodology include:
						•quoted prices for similar assets or liabilities in active markets;
						•quoted prices for identical or similar assets or liabilities in inactive markets;
						•inputs other than quoted prices that are observable for the asset or liability;
						•inputs that are derived principally from or corroborated by observable market data by correlation or other means.
						If the asset or liability has a specified (contractual) term, the Level 2 input must be observable for substantially the full term of the asset or liability.
			Level 3 —			Inputs to the valuation methodology are unobservable inputs in situations where there is little or no market activity for the asset or liability and the reporting entity makes estimates and assumptions related to the pricing of the asset or liability including assumptions regarding risk.

A financial instrument’s level within the fair value hierarchy is based on the lowest level of any input that is significant to the fair value measurement.

Common Stock and Other Exchange-Traded Equity Securities Including AECOM Stock

Mutual Funds

Self-Directed Brokerage Accounts

Fixed Income Instruments

Collective Investment Trusts

White Label Funds

INVESTMENT IN AECOM DC RETIREMENT PLANS STABLE VALUE MASTER TRUST (Details) - EBP 055 $ in Thousands	12 Months Ended
	Dec. 31, 2025 USD ($)
EBP, Change in Net Asset Available for Benefit, Increase (Decrease) from Income (Loss) on Investment [Abstract]
Interest and dividend income	$ 7,184
Net investment income	1,000,371
Beginning of year	6,778,558
End of year	7,368,267
Master Trust \| Stable Value Master Trust
EBP, Change in Net Asset Available for Benefit, Increase (Decrease) from Income (Loss) on Investment [Abstract]
Interest and dividend income	9,273
Net purchases (redemptions)	(19,214)
Administrative expenses	(9)
Net investment income	(9,950)
Beginning of year	323,734
End of year	313,784
Plan interest in Master Trust \| Stable Value Master Trust
EBP, Change in Net Asset Available for Benefit, Increase (Decrease) from Income (Loss) on Investment [Abstract]
Interest and dividend income	9,273
Net purchases (redemptions)	(19,214)
Administrative expenses	(9)
Net investment income	(9,950)
Beginning of year	323,734
End of year	$ 313,784

INVESTMENT IN AECOM DC RETIREMENT PLANS SMA MASTER TRUST (Tables)

12 Months Ended

Dec. 31, 2025

Schedule of Net Assets of the Stable Value Master Trust

The following table presents the net assets of the Vanguard Master Trust as of December 31:


	Vanguard Master Trust
	2025		2024
	(expressed in thousands)
Investments at fair value
Collective investment trusts (measured at NAV)	$	3,413,123	$	2,734,006
Mutual funds	—		630,038

Net assets of Vanguard Master Trust	$	3,413,123	$	3,364,044

The following table shows the changes in net assets for the Vanguard Master Trust for the year ended December 31:


	2025
	(expressed in thousands)
Change in net assets:
Net appreciation in fair value of investments	$	532,759
Interest and dividend income	4
Total investment income	532,763

Net purchases (redemptions)	(482,636)
Administrative expenses	(1,048)

Net increase in net assets	49,079



Net assets:
Beginning of year	3,364,044
End of year	$	3,413,123


	As of December 31, 2024
	Quoted Prices in Active Markets for Identical Assets (Level 1)		Significant Observable Inputs (Level 2)		Total Fair Value
	(expressed in thousands)
Mutual funds	$	630,038	$	—	$	630,038
Total investments in the fair value hierarchy	$	630,038	$	—	$	630,038

Investments measured at NAV					2,734,006
Total investments at fair value					$	3,364,044

Net Asset Value per Share — The following tables summarize investments measured at NAV per share as of December 31, 2025 and 2024, respectively:

December 31, 2025

Fair Value

Unfunded Commitment

Redemption Frequency (if Currently Eligible)

Other Redemption Restrictions

Redemption Notice Period

(expressed in thousands)

Retirement date funds

2,016,233

—

Daily

None

Index funds

1,396,890

—

Daily

None

December 31, 2024

Fair Value

Unfunded Commitment

Redemption Frequency (if Currently Eligible)

Other Redemption Restrictions

Redemption Notice Period

(expressed in thousands)

Retirement date funds

1,503,727

—

Daily

None

Index funds

1,230,279

—

Daily

None

The following table presents the net assets of the SMA Master Trust as of December 31:


	SMA Master Trust
	2025		2024
	(expressed in thousands)
Investments at fair value
Stocks	$	—	$	269,919
Government bonds	68,339		48,545
Corporate bonds	86,656		74,084
Mortgage-backed securities	58,570		53,807
Asset-backed securities	6,733		6,144
Collective investment trusts	401,232		257,107
Cash and cash equivalents	4,822		8,610
	626,352		718,216
Accounts receivable
Receivable for securities sold	328		596
Accrued income	1,764		1,631
Other	515		514
	2,607		2,741
Accounts payable
Due to broker for securities purchased	(3,759)		(2,538)
Operating payables	(143)		(768)
	(3,902)		(3,306)

Net assets of SMA Master Trust	$	625,057	$	717,651

The following table shows the changes in net assets for the SMA Master Trust for the year ended December 31:


	2025
	(expressed in thousands)
Change in net assets:
Net appreciation in fair value of investments and income	$	150,726

Net purchases (redemptions)	(243,199)
Administrative expenses	(121)

Net decrease in net assets	(92,594)



Net assets:
Beginning of year	717,651
End of year	$	625,057

The following tables set forth by level, within the fair value hierarchy, the SMA Master Trust assets at fair value as of December 31, 2025 and 2024:


	As of December 31, 2025
	Quoted Prices in Active Markets for Identical Assets (Level 1)		Significant Observable Inputs (Level 2)		Total Fair Value
	(expressed in thousands)
Fixed income instruments:
Asset-backed securities	$	—	$	6,733	$	6,733
Mortgage-backed securities	—		58,570		58,570
Corporate bonds	—		86,656		86,656
Government bonds	—		68,339		68,339
Stocks	—		—		—
Cash and cash equivalents	4,822		—		4,822
Total investments at fair value	$	4,822	$	220,298	225,120

Investments measured at NAV					401,232
Total investments at fair value					$	626,352


	As of December 31, 2024
	Quoted Prices in Active Markets for Identical Assets (Level 1)		Significant Observable Inputs (Level 2)		Total Fair Value
	(expressed in thousands)
Fixed income instruments:
Asset-backed securities	$	—	$	6,144	$	6,144
Mortgage-backed securities	—		53,807		53,807
Corporate bonds	—		74,084		74,084
Government bonds	—		48,545		48,545
Stocks	269,919		—		269,919
Cash and cash equivalents	8,610		—		8,610
Total investments at fair value	$	278,529	$	182,580	461,109

Investments measured at NAV					257,107
Total investments at fair value					$	718,216

Net Asset Value per Share — The following table summarizes investments measured at NAV per share as of December 31, 2025 and 2024:

December 31, 2025

Fair Value

Unfunded Commitment

Redemption Frequency (if Currently Eligible)

Other Redemption Restrictions

Redemption Notice Period

(expressed in thousands)

Arrowstreet International Equity Fund

383,294

—

Daily

None

Northern Trust All Country World ex-U.S. Index Fund

17,938

—

Daily

None

December 31, 2024

Fair Value

Unfunded Commitment

Redemption Frequency (if Currently Eligible)

Other Redemption Restrictions

Redemption Notice Period

(expressed in thousands)

Arrowstreet International Equity Fund

253,548

—

Daily

None

Northern Trust All Country World ex-U.S. Index Fund

3,559

—

Daily

None

The following table presents the net assets of the Stable Value Master Trust as of December 31:


	Stable Value Master Trust
	2025		2024
	(expressed in thousands)
Investments measured at NAV
Collective investment trust	$	313,784	$	323,734

Net assets of Stable Value Master Trust	$	313,784	$	323,734

The following table shows the changes in net assets for the Stable Value Master Trust for the year ended December 31:


	2025
	(expressed in thousands)
Change in net assets:
Interest and dividend income	$	9,273

Net purchases (redemptions)	(19,214)
Administrative expenses	(9)

Net decrease in net assets	(9,950)



Net assets:
Beginning of year	323,734
End of year	$	313,784

Net Asset Value per Share — The following table summarizes investments measured at NAV per share as of December 31, 2025 and 2024:

December 31, 2025

Fair Value

Unfunded Commitment

Redemption Frequency (if Currently Eligible)

Other Redemption Restrictions

Redemption Notice Period

(expressed in thousands)

Stable value fund

313,784

—

Daily

None

December 31, 2024

Fair Value

Unfunded Commitment

Redemption Frequency (if Currently Eligible)

Other Redemption Restrictions

Redemption Notice Period

(expressed in thousands)

Stable value fund

323,734

—

Daily

None

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.