The post has been vacant since JWT London made Steve Dunn, its former head of art and design, redundant in March 2007. Russell Ramsey, the agency's executive creative director, has taken on Dunn's duties since his exit.
Wood, who is currently the executive creative director, visual communications, at JWT New York, will join JWT London in six weeks and will have a visual influence across the board.
He will report to Ramsey and lead all print and digital design work.
Wood co-founded Tomato with six partners in 1991 after leaving Central St Martins College with a BA and MA. He joined JWT New York in 2006.
Ramsey said: "Graham is hugely talented and I'm delighted that he has decided to join us in London. He'll have an impact on everything we're doing."