The Marlins also announced on Sunday the signing of veteran catcher Sandy Leon to a minor league contract with an invitation to major league spring training. Left-hander Stephen Tarpley was designated for assignment.
Detwiler, 34, pitched in 16 games out of the bullpen for the Chicago White Sox in 2020, going 1-1 with a 3.20 ERA in 44 innings. He broke into the majors in 2007 and has a 4.56 ERA in 224 games for seven teams.
Detwiler can earn $100,000 in performance bonuses for games as a pitcher: $50,000 each for 60 and 70 games.
Leon, 31, batted .136 in 25 games last year for Cleveland. He has a .216 career average in nine seasons with three teams.