The business, which had been at Mortimer Whittaker O'Sullivan since 2004, was awarded without a pitch.
Blue Dragon has been a big spender on advertising in the past, but invested just £350,000 last year. However, the account move coincides with plans to significantly increase advertising spend in 2008.
The company, which is owned by Associated British Foods, was last on TV and in cinemas in 2005 with an animated TV spot, which ended with the line: "Release the Dragon."
Clare Pooley, a group account director at JWT, said: "We are delighted to be able to leverage our expertise in food advertising with a brand that is so innovative and on-trend. This is a great opportunity for both of us."
Peter Baxendell, the commercial director of Blue Dragon, who previously worked with JWT during his time at Unilever, added: "It's great to be working with JWT again."