The Omnicom-owned below-the-line agency said Keenleyside, who has also worked for FCB and Grey London, would be working on its accounts with Mercedes, 3, ING Direct and its newly won Dorset Cereals creative and digital brief.
He joins directly from Harrison Troughton Wunderman, where he oversaw the agency's creative campaigns for Vodafone, and will now work alongside Nick Thompson and Maxine Gregson, Claydon Heeley's creative directors.
Keenleyside is credited with a wealth of above- and below-the-line agency experience, having held positions at FCB, Grey London, TBWA Payne Stracey and Tequila. He won a silver Cannes Lions for his work with Guinness.
Pete Harle, executive creative director at Claydon Heeley, said: "Ross is a great writer, a great thinker and more importantly a great bloke. His track record speaks for itself and he will be an immense asset to the creative department and the company as a whole."