The Mets announced the move in a statement Thursday.
The 35-year-old Calero pitched for the Florida Marlins last season, going 2-2 with a 1.95 ERA in 67 relief appearances. He allowed 36 hits with 30 walks and 69 strikeouts in 60 innings, leading the Marlins' bullpen in ERA.
Calero is 14-12 with seven saves and a 3.24 ERA in 313 career games. In 302 2/3 innings, he has surrendered 236 hits with 126 walks and 324 strikeouts.