He replaces Vivian Rowden, who left Millward Brown in March to join George Patterson Bates, within the WPP Group.
Previously Dixon was executive director of Nielsen's customised business in Australia. During his nine years with the company Dixon also set up ACNielsen Online. Before joining Nielsen he worked for MRA as general manager of the business.
Mravyn Rhall, CEO of Millward Brown Africa Asia Pacific, said: "Ben's background in market research and in-depth knowledge of the Australian market will help us further develop business solutions for our Australian clients."
Dixon, who joins on September 3, said: "I am particularly excited about the opportunity at Millward Brown. The company has a very strong heritage and reputation, as well as a suite of research services that are truly focused on providing actionable insights for clients."