Pattison will help the company – founded last year by Mark Eaves, the former managing director of Drum, and Mark Boyd, Bartle Bogle Hegarty's head of content – in its growth and development strategy, and identify new business streams.
Gravity Road specialises in providing intellectual property and entertainment formats for brands.
Pattison, who left PHD in 2007 having co-founded the agency in 1990, said: "It's a real pleasure to be involved with very smart people, in a rapidly emerging and current space, who need some help along the way. My job is to act as a 'wingman' to watch the founders' and the company's backs."
Gravity Road works with clients such as Grazia and Bacardi, and recently picked up a brief to become the lead global content partnerships agency for Bombay Sapphire.