The UK-headquartered marketing services group already owns a full-service agency in Germany, SEA, through which it is buying into Leonhardt & Kern.
The deal to buy the 50-strong, Stuttgart-based agency, which has consumer-focused credentials with a client list featuring Mercedes-Benz and Lotto, the German lottery, is its first change of ownership after 40 years of trading.
Jeremy Middleton, chief executive of Media Square, said: "Expansion into continental Europe is an important part of our plan to develop the group and it will help to offset our dependency on the UK market."
The agency is being incorporated within SEA, which now employs more than 200 people and has offices in Dusseldorf, Frankfurt, Berlin, Bonn and Stuttgart.
Markus Reiser, Media Square's divisional chief executive with responsibility for continental Europe, said: "Leonhardt & Kern's consumer marketing skills, creative heritage and planning excellence will significantly strengthen SEA's overall client offering."
AIM-listed Media Square was founded in 2000 and has made a series of acquisitions across the marketing services field. In November, last year it made a significant move with the purchase of 16 marketing communications, advertising, research and online businesses from Huntsworth.
If you have an opinion on this or any other issue raised on Brand Republic, join the debate in the .