Philadelphia, which owns the best record in the Eastern Conference, built a 4-0 lead in the second period. Ilya Bryzgalov stopped 31 shots, as his lone blemish was a tap-in by Jeff Halpern with 6:01 remaining in regulation. The Flyers are now 11-3-1 on the road.
Giroux, the League's leading scorer (16 goals, 23 assists), is out indefinitely with a concussion. But the Flyers impressively provided more than enough offense without Giroux's services Tuesday night.
"I thought the guys all chipped in," Flyers coach Peter Laviolette said. "Defensively, we were good. Bryz was outstanding in net. We really covered for the guys who were missing."
Washington had its two-game winning streak snapped and fell to 3-4 under new coach Dale Hunter. The Capitals' first three losses with Hunter behind the bench were each by one goal. Washington was 7-0-3 in its previous 10 games against Philadelphia -- including a 5-2 win on Oct. 20.
The Flyers killed two Washington power plays in the first period, limited the Capitals to only five shots and took a 1-0 lead at 16:16 when Hartnell took a wrist shot from the top of the left circle that slipped between the legs of goalie Tomas Vokoun.
Hartnell has six goals and two assists during the Flyers' six-game win streak.
Philadelphia went up 2-0 at 7:23 of the second period when Bourdon took a slap shot from just inside the blue line that ticked off the stick of Capitals defenseman Mathieu Perreault and whizzed past Vokoun, who was screened by Flyers defenseman Jody Shelley. The 22-year-old Bourdon was playing in just his 10th NHL game.
"We have great practices, a great system. Everybody's stepped up," Bourdon said. "That's what a team is. Even when you're missing a player or two, you can still win."