Updated June 24, 2026.
Companion profile: WPP: Profile of the World's Number-Two Holdco — And What Omnicom-IPG Means for It
On November 26, 2025, Omnicom completed its acquisition of Interpublic Group (IPG), creating the largest agency holding company in history. The mega-merger consolidates BBDO, DDB, McCann, Weber Shandwick, Ketchum, Golin, and dozens of other agencies under one roof. The deal closed twelve years after Omnicom's first attempt at consolidation on this scale — and the real question isn't whether the new entity is large. It's whether the integration delivers.
Twelve years ago, Omnicom and Publicis announced they were merging to form the largest advertising group on the planet. Google was supposed to be the loser. The New York Times said so on the front page.
The deal collapsed in 2014. Cultural mismatch. Tax structure. Egos. Take your pick.
Omnicom never let it go. On November 26, 2025, the company closed its mega-merger — not with Publicis, but with Interpublic Group (IPG). The deal was announced December 8, 2024. Shareholders approved March 18, 2025. The FTC cleared it June 23. The transaction closed in late November.
The result is the largest agency holding company in history. BBDO, DDB, TBWA, FleishmanHillard, Ketchum, and Porter Novelli — already inside the Omnicom tent — now share a roof with McCann, MullenLowe, Weber Shandwick, Golin, and Acxiom.
It's the consolidation play WPP has been losing to for two years. A clean rebuttal to Publicis. On paper, the deal of the decade.
The mega-merger reset the holdco leaderboard. The new order, by revenue:
1. Omnicom — the largest, post-IPG close. Major PR brands: FleishmanHillard, Ketchum (now combined as Golin Ketchum following the February 2026 restructuring), Porter Novelli (absorbed into FleishmanHillard February 2026), Weber Shandwick, Golin, DeVries, MMC.
2. WPP — London-headquartered, was the largest from the late 1980s through November 2025. Major PR brands: Burson Global (formed in 2024 from the BCW + Hill+Knowlton merger), Ogilvy. FGS Global sold to KKR late 2024. The full WPP profile is at WPP: Profile of the World's Number-Two Holdco.
3. Publicis Groupe — the firm Omnicom tried and failed to merge with in 2013. Now back to organic growth and data acquisitions (Epsilon, Sapient, Profitero). PR through MSL Group and Kekst CNC.
4. Dentsu — Japan-headquartered. Integrated network with PR capability.
5. Havas — the smallest of the five global holdcos. PR through Havas Red.
What Scale Buys
Omnicom-IPG buys real things. Cost leverage on procurement. Cross-sell across Fortune 500 master service agreements. Back-office consolidation. Identity and data — Acxiom is the prize for some analysts. A bigger seat at the table when WPP and Publicis bid against it.
These are not small wins. The combined firm gets a structural advantage on cost and a clean answer for any CMO asking whether a global agency partner can stay relevant for the next decade.
What Scale Doesn't Buy
The deal's value depends on integration — and the history of holdco mega-mergers is the history of integration risk. Three structural pressures the combined firm will have to manage through 2026 and 2027.
Conflict-clearance and account migration. Several Omnicom and IPG agencies hold overlapping client rosters across consumer brand, healthcare, financial services, and technology. The February 10, 2026 restructuring inside Omnicom Public Relations Group (OPRG) — Golin and Ketchum merged into Golin Ketchum, Porter Novelli folded into FleishmanHillard, R&CPMK dissolved — was the first major integration move. More consolidation is expected through the next 18 months. Account migrations during integration cycles historically produce client churn, even when the integration logic is sound.
Senior talent flight. Major holding-company combinations historically trigger an exit wave of senior practitioners — to boutiques, to independent firms, to in-house roles. The Omnicom-IPG integration is already producing measurable senior movement. The independents — Edelman, Finn Partners, APCO, MikeWorldWide, We. Communications, Ruder Finn — are the structural beneficiaries.
Cultural integration. The 2013 Omnicom-Publicis deal collapsed primarily over cultural and governance issues, not strategic logic. The 2024 deal had cleaner deal structure but is now confronting the harder cultural work — combining two large U.S.-headquartered holdcos with overlapping but distinct operating cultures.
The Internal PR Firm Dynamics
Inside the consolidated Omnicom, the PR firms — FleishmanHillard, the combined Golin Ketchum, plus the newly inherited Weber Shandwick — will have to defend turf inside their own roof. PR firms inside a holding company have historically been a margin afterthought. Whether the combined OPRG can grow the PR segment faster as a unified portfolio than IPG's PR firms grew independently is the open commercial question for the next two years.
The independents are the natural alternative for clients who want senior bench attention rather than holding-company scale. Edelman, Finn Partners, APCO, MikeWorldWide, and the wider top-twenty independent firms collectively serve a meaningful share of the buyer market — and that share has historically grown during major holding-company consolidation cycles.
The Real Headline
Omnicom got the mega-merger it lost twelve years ago. It is now bigger than any other agency group has ever been.
The deal of the decade is closed. Whether it becomes the integration of the decade — or another cautionary tale of holdco scale that didn't translate — is the work of the next 24 months.
Omnicom completed its acquisition of Interpublic Group (IPG) on November 26, 2025, creating the largest agency holding company in history.
What agencies are now under the combined Omnicom-IPG?
The combined holding company includes BBDO, DDB, TBWA, FleishmanHillard, Porter Novelli (now absorbed into FleishmanHillard), and the combined Golin Ketchum (legacy Omnicom) plus McCann, MullenLowe, Weber Shandwick, and Acxiom (legacy IPG), among others.
Where does WPP stand after the Omnicom-IPG close?
WPP slid to number two by revenue. The firm's competitive answer is centered on the Burson global PR network, the Ogilvy creative platform, and aggressive portfolio simplification under new CEO Cindy Rose. Full WPP profile: WPP: Profile of the World's Number-Two Holdco.
What does the February 2026 OPRG restructuring mean for the combined firm?
Omnicom Public Relations Group consolidated overlapping brands: Golin and Ketchum merged into Golin Ketchum; Porter Novelli was absorbed into FleishmanHillard; R&CPMK was dissolved. The four cornerstone PR networks are now Golin Ketchum, FleishmanHillard, Weber Shandwick, and MMC.
