The deal -- 50% cash and 50% shares -- will see the B-Thinking business integrated into Ipsos China.
The agency has been running since 2003 and is based in Shanghai. It has 110 staff and operates in a market that is expected to own more cars than any other in the world by 2010.
Lifeng Liu, president of Ipsos in China, said: "Our objective in acquiring B-Thinking is to make Ipsos the leading research supplier for the automotive sector in China.
"We are now in a position to couple the client resources and experienced teams of B-Thinking with Ipsos' expertise in advertising and loyalty research."