The Mets were in need of emergency bullpen help after using seven relievers in Friday's 6-5, 14-inning loss to the Philadelphia Phillies.
The 36-year-old Carlyle has appeared in 112 career major league games, going 11-12 with a 5.58 ERA in mostly relief appearances. The right-hander struck out 25 and allowed three earned runs in 20 1/3 innings at Triple-A this season.
Montero, a rookie right-hander, was 0-2 with a 5.40 ERA in four starts this season. In 20 innings, he struck out 17 and walked 11.