Bradbury will work alongside Ben Clapp, the creative director of Tribal DDB, and Jeremy Craigen, DDB London's executive creative director, as part of the group's new integrated structure.
He will oversee all creative output for DDB WWAV, which was formed 18 months ago as a joint venture between DDB London and WWAV Rapp Collins.
Reporting to Jon Goulding, DDB WWAV's managing director, and Stephen Woodford, the chief executive of DDB London, Bradbury will also work on the integrated global accounts for Star Alliance, Getty Images and Exxon Mobil.
Goulding said: "The agency has seen exceptionally strong growth in the past 18 months, as clients demand broader communication solutions to their business challenges. We are excited to have Guy on board. He will allow us to increase this rate of change and provide the leading integrated creative product in the marketplace."
Bradbury joined RMG from Saatchi & Saatchi in January 2005. At RMG, he worked on accounts including Vodafone, HSBC and Mazda.
Woodford said: "Guy has the perfect combination of ambition and proven creative track record, and is joining us to build on DDB WWAV's fantastic success so far."