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

Rhea-AI Filing Summary

Amentum Holdings, Inc. Chief Executive Officer John E. Heller reported routine equity compensation activity involving restricted stock units and related tax withholding.

On May 6, 2026, he exercised 18,145 restricted stock units, receiving the same number of shares of common stock. To cover tax obligations upon vesting, 8,184 shares of common stock were tendered at $24.89 per share, a non-market tax-withholding disposition rather than an open-market sale.

Following these transactions, Heller directly holds 376,019 shares of Amentum common stock and 18,146 restricted stock units, each representing a contingent right to receive one share, with vesting in two equal installments on the 18-month and three-year anniversaries of the grant date.

Insights

Equity compensation analyst

CEO’s Form 4 shows routine RSU vesting, tax withholding, and continued large share ownership.

John E. Heller converted 18,145 restricted stock units into the same number of common shares on May 6, 2026. This reflects normal equity compensation vesting rather than an open-market purchase.

To satisfy tax obligations on vesting, 8,184 shares were withheld at $24.89 per share, a standard F-code transaction that does not indicate discretionary selling. Afterward, he holds 376,019 common shares directly, plus 18,146 remaining restricted stock units.

The filing indicates all derivative activity here relates to RSUs, with no remaining derivative securities listed beyond those units. Future vesting will occur in two equal tranches on the 18‑month and three‑year anniversaries of the grant date, as described in the vesting footnote.

Insider Trade Summary

18,145 shares exercised/converted

Mixed 3 txns

Insider Heller John E.

Role Chief Executive Officer

Type	Security	Shares	Price	Value
Exercise	Restricted Stock Units	18,145	$0.00	--
Exercise	Common Stock	18,145	$0.00	--
Tax Withholding	Common Stock	8,184	$24.89	$204K

Holdings After Transaction: Restricted Stock Units — 18,146 shares (Direct, null); Common Stock — 384,203 shares (Direct, null)

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. Each restricted stock unit represents a contingent right to receive one share of AMTM common stock. One-half of the restricted stock units shall vest and be delivered on the 18th month and three-year anniversaries of the date of grant.

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
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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^*

Heller John E.

(Last) (First) (Middle)

C/O AMENTUM HOLDINGS, INC.

4800 WESTFIELDS BOULEVARD, SUITE 400

(Street)

CHANTILLY VIRGINIA 20151

(City) (State) (Zip)

UNITED STATES

(Country)

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)
	Chief Executive Officer

2a. Foreign Trading Symbol

3. Date of Earliest Transaction (Month/Day/Year)
05/06/2026

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

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

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

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	05/06/2026		M		18,145	A	(1)	384,203	D
Common Stock	05/06/2026		F		8,184(2)	D	$24.89	376,019	D

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	(3)	05/06/2026		M			18,145	(4)	(4)	Common Stock	18,145	$0	18,146	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. Each restricted stock unit represents a contingent right to receive one share of AMTM common stock.

4. One-half of the restricted stock units shall vest and be delivered on the 18th month and three-year anniversaries of the date of grant.

Remarks:

	/s/ Indira Lall, Attorney-in-fact	05/07/2026
	** 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.
* Form 4: SEC 1474 (03-26)