Giordano scored into an empty net from in front of his own net with 38.4 seconds remaining to make it 3-1.
Cousins scored 1:30 into the game to put the Flyers up 1-0, and Tkachuk tied it on Calgary's second shot, at 4:28.
The Flyers, who entered having scored three times in the past four games, couldn't beat Elliott on a five-minute power play, including two full minutes at 5-on-3, when Alex Chiasson was given a major and a game-misconduct for spearing Cousins at 7:41 and Sean Monahan was called for delay-of-game at 10:33.
"I think they took momentum off of that," Cousins said. "You don't score there then it changes the whole outlook of the game. I thought they just got by there and obviously scored the next goal."