Publicis has acquired 100% of the share capital of Gravitas, which will be renamed Publicis Dialog and merged with Publicis' existing Japanese operations.
The new agency will create a shop with annual revenues in excess of £3.5m. Publicis Japan is the advertising agency formed by the French marketing services group in 1998.
Gravitas was formed in 1995 and includes Adidas, the Australian Tourist Commission and Visa International among its clients. It has a staff of 30.
Gravitas partner Sloan Carr has been named as CEO designate for Publicis Japan. He will take over the role from Louis-Sebastian Ohl after a transitional period. Ohl is set to return to a new role with Publicis in Paris.
Jeff Loucks, who runs Gravitas with Carr, has been named head of Publicis Japan.
Publicis follows in the footsteps of WPP Group, which took a stake in Japan's second-largest PR network PRAP last month. Aegis and Cordiant Communications have also made acquisitions in Japan over the past six months.
Maurice Levy, chairman and CEO of Publicis Groupe, said: "Japan is a key market for our global clients. And it is a high priority in our global expansion strategy. This acquisition is a major step in our Japanese expansion."
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