The Flyers lost despite outshooting the Panthers, 36-13, and their season-best, five-game home winning streak came to an end.
Florida goalie Scott Clemmensen made several saves in the closing seconds to hold off a Flyers flurry.
In the third period, the Flyers swarmed the net, but without any success. Scott Hartnell and Zac Rinaldo fired wide on golden chances from the slot, and Danny Briere was denied by Clemmensen on a wraparound attempt midway through the period.
Excluding an empty-net goal, the snake-bitten Briere is goalless in his last 28 games.
The game's tone was set in the first period, when the Flyers went 0 for 4 on the power play and failed to get a shot while on a five-on-three advantage for 42 seconds.
By comparison, Florida was successful on its first power-play attempt as Sean Bergenheim scored with 13:37 left in the second period, putting the Panthers ahead, 2-0. Defenseman Brian Campbell dumped a puck off the end boards, and it took a crazy bounce past Braydon Coburn and went to Begenheim, who knocked in his 17th goal.
It was the third straight game in which the Flyers had fallen into 2-0 hole. They salvaged a point against Boston on Saturday in a 3-2 shootout loss, and they jolted the hated Penguins on Sunday, 3-2, as Hartnell scored with 0.9 seconds left - their latest goal to win an overtime game in franchise history.
After Bergenheim's goal, coach Peter Laviolette called a timeout, and the Flyers responded, taking the game's next 10 shots and keeping the puck in Florida's end.
They cut the lead to 2-1, thanks to a fortuitous bounce of their own. Eric Wellwood, from behind the goal line, threw a pass out front that deflected off the right skate of Florida defenseman Ed Jovanovski and past a defenseless Clemmensen with 12:06 left in the second.
The line of Wellwood, Briere and Jakub Voracek was the Flyers' most effective unit.
Earlier, Florida took the lead as Weiss scored from the slot, rifling a high shot past Ilya Bryzgalov to the short side with 6:56 left in the first. Bryzgalov made his 16th start in the last 17 games.
Contact Sam Carchidi at email@example.com or on Twitter @BroadStBull.