Kemp batted .200 in 20 games for the Cincinnati Reds last year before breaking a rib on April 21. He then spent time in the Mets' minor league system.
Kemp, 35, is a career .285 hitter with 281 home runs in 14 seasons for four teams. He was runner-up for the NL MVP in 2011 and is a two-time Gold Glove winner.
He'll join an unsettled outfield as the Marlins continue to rebuild and audition prospects next spring under owner Derek Jeter.
The Associated Press contributed to this report.