Giroux put the Flyers ahead to stay with an unassisted goal 32 seconds into the contest and assisted on subsequent tallies by Scott Hartnell and Erik Gustafsson as Philadelphia claimed its Eastern Conference quarterfinal series 4-games-to-2.
Danny Briere also scored and Brayden Schenn added an empty-netter for the fifth-seeded Flyers, who advanced to the second round of the NHL playoffs for the third straight year.
Ilya Bryzgalov turned aside 30-of-31 shots to earn the victory after being pulled from net in Wednesday's Game 5, which the Penguins won 10-3.
The fourth-seeded Penguins could manage only Evgeni Malkin's unassisted goal, one game after the greatest offensive output in team playoff history.
Marc-Andre Fleury made 18 stops for Pittsburgh.