Gallegos was recalled from Triple-A Scranton/Wilkes-Barre on Monday.
The Yankees will go with an extra man in the bullpen for their three-game series in a National League park against the Phillies, with Gallegos called up and outfielder Clint Frazier sent down. Gallegos has made one major-league appearance this season, tossing a pair of scoreless innings. He has a 5.09 ERA in 17.2 innings at the Triple-A level, though his excellent peripherals give him a 1.84 FIP.