The role is a first for the Omnicom agency. Pritchard will take responsibility for MG OMD's social media solutions for clients including Waitrose, Specsavers and Renault. He will report to Natalie Bell, head of digital.
Pritchard began his career on MG OMD’s graduate scheme in 2006 as a radio communications manager, later becoming the first member of the social media team, as social media manager.
He returns after two years at EE, where he was latterly senior digital/social manager, working to establish EE as a leading brand on Twitter in 2012.
Bell said: "It's great to have Tim back in the agency to lead our social media offering. His enthusiasm and knowledge of the space is industry leading and I'm very excited to have him on board, leading our very successful social media teams and delivering even better social media thinking in the agency."
Last month, MG OMD hired Mark Brennan, the head of mobile at Carat, to the same role at the agency, replacing Mark Halliday.