Oskar Lindblom scored, and Martin Jones made 22 saves for the Flyers (15-26-10), who have lost six in a row.
"I think we're very frustrated," Philadelphia captain Claude Giroux said. "[We played] a good game tonight most of the time. Some lines played very well, but again in the third, we just couldn't get it done."
Lindblom tied it 1-1 at 8:09 of the third period, a shot through traffic from near the left point along the wall. Tarasenko scored 42 seconds later at 8:51, a one-timer from the slot after a pass from Robert Thomas to give St. Louis a 2-1 lead.
"We know it's a shift after we give up a goal," Tarasenko said. "We just tried to have puck possession in the [offensive] zone, control the puck. Robby [made] a nice pass; he actually made a few of those this season and I never scored before, but we made a good play, created a chance for me, and it was a good job by all five guys on the ice. All five guys got involved. It was a good goal."
On Monday, the Flyers allowed a goal 1:56 after Patrick Brown scored in the third period of a 4-3 overtime loss to the Carolina Hurricanes.
"Winning teams respond after a situation like that," Philadelphia coach Mike Yeo said. " … There's been a number of times this season, and even in this last couple weeks, where we've given up a goal the shift after a goal. Those are critical moments in the game. You've got the momentum, you have to reestablish it right away, you have to get back on your horse and get back on the attack. Obviously we got on our heels right away, and it ended up in the back of our net."