The Flyers bounced back from a 7-2 smashing at the hands of the Chicago Blackhawks 24 hours earlier to win at home for the sixth straight time.
Michael Raffi put the Flyers in front in the first period and Claude Giroux scored in the second.
Mason protected the 2-0 lead until Alex Galchenyuk beat him with a slap shot that came with 56 seconds left in regulation.
Montreal lost its second straight after winning four in a row. Carey Price stopped 25-of-27 shots in defeat.