Fields' agent, Ian Greengross, confirmed the deal Saturday. It is worth $13 million and includes $3.3 million in guaranteed money.
Fields' contract was set to expire after the 2012 season. The extension will put him under contract through 2016.
Fields, a 2007 seventh-round draft pick out of Michigan State, is coming off his best NFL season. He set single-season franchise records with a 48.8-yard average and a net of 41.4 yards.
Copyright 2012 by The Associated Press