The advertising agency landscape is undergoing its most significant restructuring in decades. The Omnicom-IPG merger, completed in late 2025, created the world's largest holding company and signaled an industry-wide shift toward consolidation and AI investment. Meanwhile, brands continue bringing capabilities in-house, putting pressure on agencies to prove their value. This FAQ explores the agency ecosystem, the forces reshaping it, and what marketers should consider when evaluating agency partners.

What is an advertising agency?

An advertising agency creates and executes advertising campaigns for clients, developing strategies to reach target audiences through various media channels. Agencies provide market research, creative development, media planning and buying, and campaign measurement.

The agency ecosystem divides into two broad categories: holding companies (large publicly traded firms controlling hundreds of agencies) and independents (standalone agencies or those owned by consultancies and tech firms). Within these categories, agencies range from full-service providers handling all aspects of advertising to hyperspecialized firms focused on areas like retail media, influencer marketing, or AI.

What are the main types of advertising agencies?

Agencies fall into three major groups regardless of holding company affiliation:

• Full-service and creative agencies. Sometimes called integrated agencies, they provide comprehensive digital and traditional advertising creative services. Examples include VML (WPP), TBWA Worldwide (Omnicom), and McCann (IPG).
• Media agencies. These specialize in planning, buying, optimizing, and measuring ad placements. They handle functions downstream of creative, including programmatic buying and cross-channel attribution. Examples include Mindshare (WPP), OMD Worldwide (Omnicom), and Starcom (Publicis).
• Specialized agencies. This category includes firms focused on AI, data and CRM, healthcare, multicultural marketing, retail media, social media, and influencer marketing.

What is an advertising holding company?

An advertising holding company is a publicly traded firm that owns and operates dozens of subsidiary agencies, often organized into clusters by specialty. These companies provide clients access to a wide range of services through their agency networks, from creative and media to data, commerce, and public relations.

The industry has historically referenced "The Big Six" holding companies: WPP, Omnicom, Publicis Groupe, Interpublic Group (IPG), Dentsu, and Havas. Stagwell, formed from the 2021 merger of MDC Partners and Stagwell Marketing Group, represents a newer entrant. The Omnicom-IPG merger, completed in late 2025, consolidated this group further.

How has the Omnicom-IPG merger reshaped the agency landscape?

The merger made Omnicom the largest holding company by revenue, displacing WPP from the top position it held for years. Key changes include:

• Network consolidation. Omnicom retired agency networks FCB, MullenLowe, and DDB. The company now operates three global creative networks: McCann, BBDO, and TBWA.
• Workforce reductions. An estimated 4,000 positions were eliminated worldwide, with $750 million in expected cost savings within two years.
• Data integration. The merger combines IPG's Acxiom with Omnicom's Flywheel commerce platform, creating expanded first-party data capabilities.
• AI infrastructure. Enterprise generative AI sits at the core of Omnicom's new value proposition, with all teams gaining access to its Omni intelligence platform, per EMARKETER.

Why are advertising agencies consolidating?

Several forces are driving agency consolidation in 2026:

• AI capital requirements. Building enterprise-grade AI capabilities requires significant investment. Omnicom, WPP, Publicis, and others have committed hundreds of millions to AI development. Scale helps amortize these costs.
• Declining market share. The Big Six's share of US ad spending dropped to 29.6% in Q1 2024, down from 44.6% in 2019, according to Advertiser Perceptions data cited by EMARKETER. Since 2023, worldwide media ad spending has grown faster than average revenues at these holding companies, according to EMARKETER.
• Client demand for integration. Advertisers increasingly want unified services spanning creative, media, data, and commerce, rather than managing multiple agency relationships.
• Margin pressure. Competition from consultancies, in-house teams, and technology platforms squeezes agency profitability, making consolidation attractive for cost reduction.

What challenges do ad agencies face?

Agencies face pressure from two directions: AI disruption and brand in-housing.

AI disruption: Generative AI performs tasks that previously required teams of copywriters, designers, and media buyers. 60% of US senior marketing leaders said they spend less on agencies in 2025 as a direct result of AI, according to a Typeface survey. Platforms like Meta, Google, and TikTok are advancing their own AI ad-creation tools, potentially disintermediating agencies.

In-housing: The Association of National Advertisers’ (ANA’s) most recent report on in-housing, published in 2023, found that 82% of the organization’s members reported having an in-house agency, up from 78% in 2018.This trend leaves agencies scrambling to prove their value beyond services brands can build internally.

Major holding companies have committed substantial capital to AI development. WPP partnered with Nvidia on an AI-enabled content creation engine in 2023, Publicis Groupe launched an internal AI tool in 2018, and IPG integrates Adobe's GenStudio across its agency portfolio.

These investments target use cases across the advertising lifecycle: ideation, research, content drafting, ad production, process automation, and campaign optimization. Omnicom's merger with IPG explicitly positioned enterprise AI as the combined company's core value proposition, according to EMARKETER.

How should marketers evaluate agency partners in 2026?

Marketers evaluating agency relationships should assess four areas:

1. AI capabilities. What generative AI tools does the agency deploy? Can it demonstrate efficiency gains and creative applications? Agencies without mature AI infrastructure will struggle to compete on speed and cost.
2. Data assets. Does the agency offer access to first-party data for targeting and measurement? The Omnicom-IPG combination of Acxiom and Flywheel illustrates how holding companies are building data moats.
3. Integration vs. specialization. Consolidated holding companies offer end-to-end services, while specialized independents may provide deeper expertise in specific channels. Match structure to your needs.
4. Transparency. The ANA has raised concerns about principal media buying practices. Clarify how your agency sources inventory and where markups apply.

The agency landscape in 2026 rewards those with scale, AI fluency, and proprietary data. Marketers should consider whether their agency partners can deliver on all three.

We prepared this article with the assistance of generative AI tools and stand behind its accuracy, quality, and originality.

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