Kelly turns 36 on Feb. 15. He appeared in only two games with the Marlins last season, going hitless in one at-bat.
He appeared in 545 games with Detroit from 2009 through 2014, and broke into the majors with Pittsburgh in 2007. Kelly is a lifetime .232 hitter, with 23 home runs and 95 RBIs.
The Marlins now have 63 players invited to camp, which begins later this month.