Attik was founded in the UK in 1986 by Simon Needham and James Sommerville as a graphic design agency. Now headquartered in Leeds, it has evolved into a branding and creative agency with clients including Adidas, Coca-Cola and Heineken. It also publishes the NoiseFive series of experimental design books.
It has expanded to the US and made a name for itself with the campaign to launch Toyota's Scion brand in 2003. Its US offices are in San Francisco, Los Angeles and New York and its other clients include Boost Mobile and ExpressJet Airlines.
Hiromi Yoshida, president of Dentsu Holdings USA, said: "Attik is part of the continuation of Dentsu acquiring and developing diversified agency services."
Sommerville will stay on as creative director of Attic UK and Needham as creative director in the US.
Ric Peralta and William Travis, formerly the chief executive and president of Attic US, have become president and vice-president of Attic Division, Dentsu America.
Sommerville said: "We have never stood still since we began chalking on the streets of Huddersfield and Manchester in the mid-80s. It's been an incredible journey that has seen us transform ourselves many times."