Lewis, who joined the brewer five years ago from Carlsberg where he was marketing controller, leaves Wells & Young's on Thursday 31st May.
During his time at the brewer, Lewis oversaw new advertising for Bombardier beer, featuring actor Rik Mayall and created by Karmarama. He also rolled out new marketing for Estrella Damm.
Lewis said: "It's never easy to leave a company where you have had so much time and respect for the people and the brands, but there comes a point where you know the time is right to seek out new challenges.
A spokeswoman for Wells & Young's Brewing Company said no decision had been taken on a replacement for Lewis or the future structure of the marketing team.