[Form 4] Omnicom Group Inc. Insider Trading Activity

Rhea-AI Filing Summary

Andrew Castellaneta, SVP and Chief Accounting Officer of Omnicom Group Inc. (OMC), sold 1,850 shares of Omnicom common stock on 08/15/2025 at $76.31 per share. After the sale, he beneficially owned 21,875 shares. The reported ownership total includes 4,097 shares acquired under Omnicom's employee stock purchase plan.

The Form 4 was signed by Eric J. Cleary as Attorney in Fact for Mr. Castellaneta on 08/19/2025. The filing indicates the transaction type code "F" and reports direct ownership following the transaction.

Positive

• Transparent disclosure of the officer's sale and remaining beneficial ownership.
• Inclusion of ESPP shares (4,097) clarifies composition of holdings.

Negative

• None.

Insights

Securities Analyst

TL;DR: A routine officer sale of 1,850 OMC shares at $76.31, leaving 21,875 shares held; appears non-material to company operations.

The sale recorded under transaction code "F" shows an officer reduction of personal holdings but does not include any derivative transactions or indications of unusual activity. The reported remaining beneficial ownership of 21,875 shares provides transparency on insider stake size. No additional compensatory or non-routine disclosures are present in this Form 4.

Corporate Governance Expert

TL;DR: Filing documents a standard insider sale executed via direct disposition, with ESPP holdings noted; governance disclosure appears complete.

The Form identifies the reporting person, role (SVP, Chief Accounting Officer), and relationship to the issuer, and includes an explanation that 4,097 shares were acquired under the employee stock purchase plan. The signature by an attorney-in-fact is provided with a date, satisfying procedural requirements for Section 16 reporting.

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^*

Castellaneta Andrew

(Last) (First) (Middle)

C/O OMNICOM GROUP INC.

280 PARK AVENUE

(Street)

NEW YORK NY 10017

(City) (State) (Zip)

2. Issuer Name and Ticker or Trading Symbol
OMNICOM GROUP INC. [ OMC ]

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

	Director		10% Owner
X	Officer (give title below)		Other (specify below)
	SVP, Chief Accounting Officer

3. Date of Earliest Transaction (Month/Day/Year)
08/15/2025

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, par value $0.15 per share	08/15/2025		F		1,850	D	$76.31	21,875(1)	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

Explanation of Responses:

1. Includes 4,097 shares acquired under Omnicom's employee stock purchase plan.

	/s/ Eric J. Cleary, Attorney in Fact for Andrew Castellaneta	08/19/2025
	** 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.

FAQ

What did Andrew Castellaneta sell and when (OMC)?

He sold 1,850 shares of Omnicom common stock on 08/15/2025 at $76.31 per share.

How many Omnicom (OMC) shares does the reporting person own after the sale?

21,875 shares beneficially owned following the reported transaction.

Does the Form 4 report any option or derivative activity for OMC?

No. Table II for derivative securities shows no entries; only a non-derivative sale is reported.

What portion of the reported holdings came from the employee stock purchase plan (OMC)?

4,097 shares are noted as acquired under Omnicom's employee stock purchase plan.

Who signed the Form 4 for Andrew Castellaneta (OMC) and when?

Eric J. Cleary, Attorney in Fact, signed the Form on 08/19/2025.