Cover and table of contents

UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

FORM 10-K

☑ ANNUAL REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934

FOR THE FISCAL YEAR ENDED DECEMBER 31, 2025

Commission File Number: 1-10551

Omnicom Group Inc.

(Exact name of registrant as specified in its charter)

Registrant’s telephone number, including area code: (212) 415-3600

Securities Registered Pursuant to Section 12(b) of the Act:

Securities Registered Pursuant to Section 12(g) of the Act: None

Indicate by check mark if the registrant is a well-known seasoned issuer, as defined in Rule 405 of the Securities Act. Yes þ No o

Indicate by check mark if the registrant is not required to file reports pursuant to Section 13 or Section 15(d) of the Act. Yes o No þ

Indicate by check mark whether the registrant (1) has filed all reports required to be filed by Section 13 or 15(d) of the Securities Exchange Act of 1934 during the preceding 12 months (or for such shorter period that the registrant was required to file such reports), and (2) has been subject to such filing requirements for the past 90 days. Yes þ No o

Indicate by check mark whether the registrant has submitted electronically every Interactive Data File required to be submitted pursuant to Rule 405 of Regulation S-T (§ 232.405 of the chapter) during the preceding 12 months (or for such shorter period that the registrant was required to submit such files). Yes þ No o

Indicate by check mark whether the registrant is a large accelerated filer, an accelerated filer, a non-accelerated filer, a smaller reporting company or an emerging growth company. See the definitions of “large accelerated filer,” “accelerated filer,” “smaller reporting company” and “emerging growth company” in Rule 12b-2 of the Exchange Act.

If an emerging growth company, indicate by check mark if the registrant has elected not to use the extended transition period for complying with any new or revised financial accounting standards provided pursuant to Section 13(a) of the Exchange Act. o

Indicate by check mark whether the registrant has filed a report on and attestation to its management’s assessment of the effectiveness of its internal control over financial reporting under Section 404(b) of the Sarbanes-Oxley Act (15 U.S.C. 7262(b)) by the registered public accounting firm that prepared or issued its audit report. ☑

If securities are registered pursuant to Section 12(b) of the Act, indicate by check mark whether the financial statements of the registrant included in the filing reflect the correction of an error to previously issued financial statements. ☐

Indicate by check mark whether any of those error corrections are restatements that required a recovery analysis of incentive-based compensation received by any of the registrant’s executive officers during the relevant recovery period pursuant to § 240.10D-1(b). o

Indicate by check mark whether the registrant is a shell company (as defined in Rule 12b-2 of the Act). Yes ☐ No þ

The aggregate market value of the voting and non-voting common stock held by non-affiliates as of June 30, 2025 was $13,815,889,740. As of January 30, 2026, there were 310,336,344 shares of Omnicom Group Inc. Common Stock outstanding.

Portions of the Omnicom Group Inc. Definitive Proxy Statement for the Annual Meeting of Shareholders planned to be held on May 5, 2026 are incorporated by reference into Part III of this report to the extent described herein.

OMNICOM GROUP INC.

ANNUAL REPORT ON FORM 10-K FOR THE YEAR ENDED DECEMBER 31, 2025

TABLE OF CONTENTS

i

FORWARD-LOOKING STATEMENTS

This Annual Report on Form 10-K contains forward-looking statements, including statements within the meaning of the Private Securities Litigation Reform Act of 1995, as amended. In addition, from time to time, we or our representatives have made, or may make, forward-looking statements, orally or in writing. These statements, other than statements of historical fact, may discuss goals, intentions and expectations as to future plans, trends, events, results of operations or financial condition, or otherwise, based on current beliefs of our management as well as assumptions made by, and information currently available to, our management. Forward-looking statements may be accompanied by words such as “aim,” “anticipate,” “believe,” “plan,” “could,” “should,” “would,” “estimate,” “expect,” “forecast,” “future,” “guidance,” “intend,” “may,” “will,” “possible,” “potential,” “predict,” “project” or similar words, phrases or expressions. These forward-looking statements are subject to various risks and uncertainties, many of which are outside our control. Therefore, you should not place undue reliance on such statements. Factors that could cause actual results to differ materially from those in the forward-looking statements include:

• risks relating to the completed merger (the “Merger”) between us and The Interpublic Group of Companies, Inc. (IPG), including risks related to the integration of IPG’s business, such as, among others: uncertainties associated with retaining key management and other employees; potential disruptions to client, vendor, and business partner relationships; the risk that integration activities may be more time-consuming, complex, or costly than expected; the possibility that anticipated synergies, efficiencies, and other benefits of the Merger may not be realized, or may be realized more slowly than anticipated; and risks associated with managing a larger, more complex combined organization and effectively integrating systems, processes, operations, and cultures;

• adverse economic conditions, including geopolitical events, international hostilities, acts of terrorism, public health crises, inflation or stagflation, tariffs and other trade barriers, central bank interest rate policies in countries that comprise our major markets, labor and supply chain issues affecting the distribution of our clients’ products, or a disruption in the credit markets;

• international, national or local economic conditions that could adversely affect us or our clients;

• reductions in client spending, a slowdown in client payments or a deterioration or disruption in the credit markets;

• the ability to attract new clients and retain existing clients in the manner anticipated;

• changes in client marketing and communications services requirements;

• failure to manage potential conflicts of interest between or among clients;

• unanticipated changes related to competitive factors in the marketing and communications services industries;

• unanticipated changes to, or an inability to hire and retain, key personnel;

• currency exchange rate fluctuations;

• reliance on information technology systems and risks related to cybersecurity incidents;

• effective management of the risks, challenges and efficiencies presented by utilizing artificial intelligence, or AI, technologies and related partnerships in our business, and their use by our competitors;

• failure to adapt to technological developments;

• our liquidity, long-term financing needs, credit ratings and access to capital markets;

• changes in legislation or governmental regulations affecting us or our clients;

• losses on media purchases and production costs incurred on behalf of clients;

• risks associated with assumptions we make in connection with our acquisitions, critical accounting estimates and legal proceedings;

• our international operations, which are subject to the risks of currency repatriation restrictions, social or political conditions and an evolving regulatory environment in high-growth markets and developing countries;

• risks related to our environmental, social and governance goals and initiatives, including impacts from regulators and other stakeholders, and the impact of factors outside of our control on such goals and initiatives;

• changes in tax rates, tax laws, regulations or interpretations, or adverse outcomes of tax audits or proceedings; and

• other business, financial, operational and legal risks and uncertainties detailed from time to time in our filings with the Securities and Exchange Commission (SEC).

The foregoing list of factors is not exhaustive. You should carefully consider the foregoing factors and the other risks and uncertainties that may affect our business, including those described in Item 1A., “Risk Factors” and Item 7., “Management’s Discussion and Analysis of Financial Condition and Results of Operations”, or MD&A, in this report and in other documents filed from time to time with the SEC. Except as required under applicable law, we do not assume any obligation to update these forward-looking statements.

ii

PART I

Introduction

This report is our 2025 annual report to shareholders and our 2025 Annual Report on Form 10-K, or 2025 10-K.

Omnicom Group Inc., a New York corporation, was formed in 1986. The terms “Omnicom”, “the Company”, “we”, “our” and “us” each refer to Omnicom Group Inc. and its subsidiaries unless the context indicates otherwise.