The answer depends on what you call an agency, and that is not word play: the counts differ by a factor of ten.
Three counts, three answers
1.217 agencies sit in IKAg's database, for Belgium and the Netherlands together. These are the agencies we track: creative, media, digital, PR, activation and the specialists in between.
1,018 Belgian agencies filed at least one readable set of annual accounts since 2021, together good for 4,242 financial years.
804 agencies were active in financial year 2024 in the sense that matters: a gross margin above 50,000 euro. That is the threshold the Agency Barometer uses, and it separates an agency from a one-person sideline.
Count every company that calls itself a communication agency and you reach the thousands. That count is correct and useless: the vast majority have one or two people and will never be on your longlist.
Why you only ever hear thirty names
The market is narrow at the top. A handful of network agencies and a few dozen independents do the most visible work, and those are the names that come up in every meeting. Below them lies a long tail of small agencies, and that is exactly where the specialists sit who often fit a specific brief better.
Which is also why a longlist should rarely start with the names you know: you build it on what you need, not on who you have heard of.
How to search this market
IKAg's factsheets are open: you can browse by expertise, by sector, by location and by group. Each agency shows its services, reference clients, awards and the figures from its filed annual accounts.
See also: what types of agency exist, how big the average agency is and how to find a good agency.