What is the biggest marketing agency in the US?
The biggest US-headquartered marketing/advertising agencies by revenue are inside the Omnicom Group (BBDO, TBWA, DDB, PHD) and Interpublic Group (McCann, IPG Mediabrands). Individual brands within these holding groups regularly bill $500M–$1B+ annually. Ogilvy (WPP), Wieden+Kennedy (independent), and R/GA (Interpublic) round out the top of the US market.
What the index holds at the top end
The Wall indexes independent US firms and does not rank them, so it has no single name to give. The shape of the market is more useful anyway. 2,912 listings publish a team size. 52 of them run 1,000 people or more and 165 run 250 or more.
2,361 run fewer than 50, which is 81% of everyone publishing a figure. The US marketing services industry is a very large number of very small companies.
Age tracks size more closely than anything else in the data. 348 of the 2,800 listings that publish a founding year opened before 2000, and the median across the whole index is 2013. The firms at the top of the size distribution mostly got there by lasting.
How to use this
If a vendor's size is doing the reassuring in a pitch, ask what it changes about your account. Usually it changes bench depth and nothing else, and bench depth only matters if your scope swings.
How this was computed. Every figure on this page is counted from The Wall's own directory of approved, US-headquartered, machine-verified-live listings: 3,460 of them in the snapshot captured 2026-09-14. Rates, minimum project sizes, team sizes, founding years and ratings are provider-declared figures published on public profiles. 1,738 of those listings publish a service list, and that field holds at most 4 services per firm, so service counts are counts of what firms name first rather than everything they sell. Percentages of disclosed values exclude listings that publish no figure. Nothing here is modeled or estimated. Sourcing standards: editorial policy.
Why this matters
Google puts this question in People Also Ask for the "marketing agency" query, which means buyers are asking it while they shop. The Wall answers it from the directory position: we index 3,460 verified US growth-services vendors across 10 pillars, so the figures above come from those records rather than from a survey.
If you are evaluating vendors in this category, the Marketing pillar page carries the full US firm list with rate, team size and headquarters filters.