Weeks, 28, who played just 37 games in 2009 because of injuries, belted 28 home runs, scored 110 runs and drove in 81 last year from the leadoff spot in the batting order.
Financial terms of the deal were not disclosed, although media reports said that with an option year it could be worth $50 million over five years.
"We are thrilled that Rickie has chosen to remain a Brewer," general manager Doug Melvin said in a statement. "He has become one of the best leadoff hitters in the game today."
(Writing by Larry Fine, Editing by Steve Ginsburg)