The Devils won despite squandering a 2-0 lead. It was Clemmensen's third career shootout; he was 1-1 in the previous two.
New Jersey defeated Philadelphia for the first time in four meetings this season. The Devils (19-9-3) pulled within two points of the Flyers (18-9-6) in the Atlantic Division standings, behind the division-leading New York Rangers.
After a scoreless first period, the Devils broke into the scoring column midway through the second period on a power play opportunity. Patrik Elias skated in on the left side unguarded and knocked home a rebound of a slap shot by Travis Zajac at the 7:30 mark. It was Elias' 16th goal of the season.
Just 1:06 later, Brian Rolston, who recently returned after missing more than a month with a high ankle sprain, scored his second goal in the last three games, with assists going to David Clarkson and Bobby Holik.
The Flyers then sliced the lead in half when Jeff Carter scored on the power play with 2:42 remaining in the period. Carter was untouched in front of the goal and his alert shot fired past Clemmensen for his 25th goal of the season.
Clemmensen started in goal for the fourth straight game and 12th in 13 in place of injured All-Star Martin Brodeur. With 14 minutes left in regulation, he stuffed a breakaway attempt by Scott Hartnell, who skated in and attempted a backhand toward Clemmensen.
Clemmensen, who had 27 saves, slid across the crease to stop the shot. The Devils looked to have the game in hand, but then Carter made a big play late in the game.
With 4:44 left in the third, Carter skated into the corner and lifted a backhanded pass in front to Joffrey Lupul, who slid the puck past Clemmensen for the game-tying goal. It was Lupul's 12th goal of the season and it sent the game into overtime.
Clemmensen had the biggest save in overtime, when he snuffed Carter from point-blank range with 1:54 remaining in the extra session.
NOTES: Devils standout defensive forward John Madden sat out for the second straight game with flu-like symptoms, while defenseman Bryce Salvador was a scratch due to an undisclosed upper body injury. Madden is expected to return when the Devils host Eastern Conference leader Boston on Tuesday night. Salvador's return to action is still undetermined. ... Center Glen Metropolit, defenseman Lasse Kukkonen and defenseman Luca Sbisa were scratches for the Flyers, who started Antero Niittymaki in goal instead of Martin Biron. It was only the 14th appearance of the season for Niittymaki.