Gray will report to the executive creative director, Robert Campbell, who has made a series of high-profile hirings since he joined in January in a bid to improve the agency's creative reputation.
Gray will work with Brian Fraser, Simon Learman, Stephen Ward, John Hurst and Marc Bennet. A further creative director is expected to be added to the team. Gray has spent the past two years out of the industry writing children's books. He was recently named among the top-ten children's authors by The Independent. His last job in advertising was at Saatchis where he was a senior writer between 1994 and 2002, working with the art director Jonathan Greenhalgh.
They created the "full stop" campaign for the NSPCC. However, the pair is best remembered for the Carling Black Label "dambusters" spots, which they created at WCRS, where they worked between 1992 and 1994.
They joined the agency from BMP DDB Needham after a spell at Chiat Day.
Campbell said: "Kes is unquestionably one of the greats. We're thrilled he's to join the team at McCann."
Gray added: "Something very special is happening at McCann Erickson and I want to be a part of it. The management line-up is awesome and their ambition is tangible. I can't wait to start."