Bolton, who left JWT in November last year, takes over from Dave Allen.
Allen will become the chief executive of Team Vodafone.
In his new role, Bolton will be responsible for expanding the consultancy into new markets. It has a client list including BP, Credit Suisse and Unilever and currently operates across North America and Asia.
Craig Branigan, the head of the Branding Identity and Design Group at WPP, said: "Simon has the skills to motivate people and build businesses.
"He has a good knowledge of WPP and is very familiar with the US and Asian markets, where the growth potential for Enterprise IG is huge."
Before joining JWT, Bolton was the president and chief executive of Foote Cone & Belding in San Francisco. He has also worked at FCB Malaysia, where he was responsible for managing acquisition and development across South-East Asia.
Allen, one of the founding members of Enterprise IG, will now co-ordinate all of the WPP companies working on the Vodafone account.