Craig Williams added 11 points for the Owls (18-11, 10-5 Atlantic 10), who defeated Saint Joe's for the fourth straight time.
Temple led 34-23 two minutes into the second half, but the Hawks scored 9 straight points capped by a Nivins slam to trail by 34-32.
Christmas and Williams hit 3-pointers, igniting a 13-0 spurt and a 47-32 Temple edge with 11 minutes to go. Saint Joseph's closed to 52-45 with 4:29 remaining, but Christmas made a nifty pass to Olmos for a layup, then hit a trey to put the game out of reach.
Christmas and Nivins went into the game tied for the league's scoring lead at 19 points per game.