Willmott will oversee creative on all UK business, and work across a number of yet-to-be-determined European accounts.
He will also take an active role in new business, reporting to Michael Bray, the president of DDB Europe.
Willmott joins from JWT, where he has been the global creative director on Vodafone since October 2006. He joined JWT from Publicis New York, where he was the executive creative director.
During his career, he has won eight D&AD Pencils and 11 Cannes Lions for work including the "cartoon" spot for the NSPCC.
Stephen Woodford, the chairman and chief executive of DDB, said: "This is a new role for DDB and reflects London's role as a key hub for global business.
With Howard's arrival and our other recent hirings, we have strengthened our team with some of the best and most experienced players in the market."
Earlier this month, Nick Bell, the former executive creative director of JWT, joined DDB as a global creative director working on its Unilever-owned Lipton business (Campaign, 14 March).