[Form 4] Amentum Holdings, Inc. Insider Trading Activity

Rhea-AI Filing Summary

Amentum Holdings, Inc. (AMTM) reported insider equity activity by its Executive Chair and director on Form 4 dated 11/17/2025. The insider received 43,396 shares of AMTM common stock upon vesting of previously granted restricted stock units and had 17,077 shares of common stock tendered to cover tax withholding related to that vesting at a price of $21.49 per share. The insider was also granted 111,355 restricted stock units that will vest and be delivered on the first anniversary of November 17, 2025. Following these transactions, the insider beneficially owned 820,476 shares of AMTM common stock directly and 23,550 shares indirectly through a spouse.

Insider Trade Summary

43,396 shares exercised/converted

Mixed 5 txns

Insider DEMETRIOU STEVEN J.

Role Executive Chair

Type	Security	Shares	Price	Value
Exercise	Restricted Stock Units	43,396	$0.00	--
Exercise	Common Stock	43,396	$0.00	--
Tax Withholding	Common Stock	17,077	$21.49	$367K
Grant/Award	Common Stock	111,355	$0.00	--
holding	Common Stock	--	--	--

Holdings After Transaction: Restricted Stock Units — 0 shares (Direct); Common Stock — 726,198 shares (Direct); Common Stock — 23,550 shares (Indirect, By Spouse)

Footnotes (1)

1. Represents distribution of AMTM common stock upon vesting of restricted stock units. Represents number of shares of AMTM common stock tendered for tax withholding upon vesting of restricted stock units. The restricted stock units shall vest and be delivered on the first anniversary of November 17, 2025. Each restricted stock unit represents a contingent right to receive one share of AMTM common stock. The restricted stock units awarded vested on November 17, 2025.

Form 4 Insider Transactions: What Each Field Means →

SEC Form 4

FORM 4

UNITED STATES SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549

STATEMENT OF CHANGES IN BENEFICIAL OWNERSHIP

Filed pursuant to Section 16(a) of the Securities Exchange Act of 1934
or Section 30(h) of the Investment Company Act of 1940

OMB APPROVAL

OMB Number:			3235-0287
Estimated average burden
hours per response:			0.5

Check this box if no longer subject to Section 16. Form 4 or Form 5 obligations may continue. See Instruction 1(b).

Check this box to indicate that a transaction was made pursuant to a contract, instruction or written plan for the purchase or sale of equity securities of the issuer that is intended to satisfy the affirmative defense conditions of Rule 10b5-1(c). See Instruction 10.

1. Name and Address of Reporting Person^*

DEMETRIOU STEVEN J.

(Last) (First) (Middle)

C/O AMENTUM HOLDINGS, INC.

4800 WESTFIELDS BOULEVARD, SUITE 400

(Street)

CHANTILLY VA 20151

(City) (State) (Zip)

2. Issuer Name and Ticker or Trading Symbol
Amentum Holdings, Inc. [ AMTM ]

5. Relationship of Reporting Person(s) to Issuer
(Check all applicable)

X	Director		10% Owner
X	Officer (give title below)		Other (specify below)
	Executive Chair

3. Date of Earliest Transaction (Month/Day/Year)
11/17/2025

4. If Amendment, Date of Original Filed (Month/Day/Year)

6. Individual or Joint/Group Filing (Check Applicable Line)

X	Form filed by One Reporting Person
	Form filed by More than One Reporting Person

Table I - Non-Derivative Securities Acquired, Disposed of, or Beneficially Owned
1. Title of Security (Instr. 3)	2. Transaction Date (Month/Day/Year)	2A. Deemed Execution Date, if any (Month/Day/Year)	3. Transaction Code (Instr. 8)		4. Securities Acquired (A) or Disposed Of (D) (Instr. 3, 4 and 5)			5. Amount of Securities Beneficially Owned Following Reported Transaction(s) (Instr. 3 and 4)	6. Ownership Form: Direct (D) or Indirect (I) (Instr. 4)	7. Nature of Indirect Beneficial Ownership (Instr. 4)
			Code	V	Amount	(A) or (D)	Price
Common Stock	11/17/2025		M		43,396	A	(1)	726,198	D
Common Stock	11/17/2025		F		17,077(2)	D	$21.49	709,121	D
Common Stock	11/17/2025		A		111,355(3)	A	$0	820,476	D
Common Stock								23,550	I	By Spouse

Table II - Derivative Securities Acquired, Disposed of, or Beneficially Owned (e.g., puts, calls, warrants, options, convertible securities)
1. Title of Derivative Security (Instr. 3)	2. Conversion or Exercise Price of Derivative Security	3. Transaction Date (Month/Day/Year)	3A. Deemed Execution Date, if any (Month/Day/Year)	4. Transaction Code (Instr. 8)		5. Number of Derivative Securities Acquired (A) or Disposed of (D) (Instr. 3, 4 and 5)		6. Date Exercisable and Expiration Date (Month/Day/Year)		7. Title and Amount of Securities Underlying Derivative Security (Instr. 3 and 4)		8. Price of Derivative Security (Instr. 5)	9. Number of derivative Securities Beneficially Owned Following Reported Transaction(s) (Instr. 4)	10. Ownership Form: Direct (D) or Indirect (I) (Instr. 4)	11. Nature of Indirect Beneficial Ownership (Instr. 4)
				Code	V	(A)	(D)	Date Exercisable	Expiration Date	Title	Amount or Number of Shares
Restricted Stock Units	(4)	11/17/2025		M(1)			43,396	(5)	(5)	Common Stock	43,396	$0	0	D

Explanation of Responses:

1. Represents distribution of AMTM common stock upon vesting of restricted stock units.

2. Represents number of shares of AMTM common stock tendered for tax withholding upon vesting of restricted stock units.

3. The restricted stock units shall vest and be delivered on the first anniversary of November 17, 2025.

4. Each restricted stock unit represents a contingent right to receive one share of AMTM common stock.

5. The restricted stock units awarded vested on November 17, 2025.

Remarks:

	/s/ Mark Esposito, Attorney-in-Fact	11/19/2025
	** Signature of Reporting Person	Date
Reminder: Report on a separate line for each class of securities beneficially owned directly or indirectly.
* If the form is filed by more than one reporting person, see Instruction 4 (b)(v).
** Intentional misstatements or omissions of facts constitute Federal Criminal Violations See 18 U.S.C. 1001 and 15 U.S.C. 78ff(a).
Note: File three copies of this Form, one of which must be manually signed. If space is insufficient, see Instruction 6 for procedure.
Persons who respond to the collection of information contained in this form are not required to respond unless the form displays a currently valid OMB Number.