In his new role, Douglas will take responsibility for making communications planning an integral part of the agency's creative process.
He replaces Simon Summerscales, who left W&K a month ago to take a break from the industry.
Douglas will report to Martin Cole, who was hired last week as the planning director.
Cole's appointment followed the departure of the former planning director Stuart Smith, who left W&K in August to join Google's New York-based creative agency, Google Creative Lab, as its planning director.
Douglas, who will take up his new role in January 2009, began his career at Equinox Communications in 2000, before moving to ZenithOptimedia in 2003. He joined Carat in 2005, and was promoted to strategy director two years later.
Neil Christie, W&K's managing director, said: "We're delighted. Graeme shares our belief that innovative media thinking should be at the heart of the creative process."