Kris Letang also had a third-period goal for Pittsburgh, which earned its fifth straight win.
"We were 4-0 without him, so we were going to tell him to stay home," joked Pittsburgh goalie Marc-Andre Fleury, who stopped 31 shots. "No, he's an important player, he's our captain, a good leader, a good worker. It's good to have him back."
Bill Guerin, traded to Pittsburgh from the New York Islanders on Wednesday, had an assist on Crosby's goal. Crosby missed Pittsburgh's last four games because of a groin injury, and skated on a new line with Guerin and Chris Kunitz, also acquired in a trade while Crosby was out with the injury.
"Both (Guerin) and Kunitz did a great job tonight and we're still learning from each other," Crosby said. "We can still create more. We'll figure some chemistry there."
Radek Dvorak scored for Florida, coming off a five-game trip.
Tomas Vokoun made 43 saves for Florida, which is 17-8-3 since Jan. 1.
"They had good legs, they had good jump. They beat us to a lot of loose pucks," Panthers coach Pete DeBoer said. "We looked like a team that came off a nine-day road trip. We hung in there for a little while and Tomas gave us a chance to hang around, but the better team won. We got what we deserved."
Kennedy broke a 1-1 tie at 2:24 in the third period. He scored on a one-timer from the right circle after taking a pass from Matt Cooke. Letang made it 3-1 at 4:37 in the final period with a wrist shot.
Kennedy scored again with 4:26 left in the third period on a 2-on-1 when he one-timed a feed from Evgeni Malkin to make it 4-1.
"They played well," Vokoun said. "We just weren't able to contain them and they outplayed us. Sometimes that's going to happen."
Dvorak gave the Panthers a 1-0 lead with 2:11 left in the second period. Gregory Campbell passed the puck to Dvorak, and his redirection from the side of the net trickled under Fleury's arm.
It didn't take long for Crosby to tie it at 1-all. Just 26 seconds after Dvorak's goal, Crosby split Florida defensemen Jay Bouwmeester and Karlis Skrastins and beat Vokoun with a wrist shot from the left faceoff circle.
"That's a huge answer," Penguins interim coach Dan Bylsma said. "We played a pretty good game up to that point. They get that first goal and it could be a deflater, but the captain answers right back with a great goal. Kind of a signature goal for Sidney in this building. He's gone through the D here and scored before. That was a big answer. The telephone was ringing and that was a big answer."
The Penguins are in the midst of a five-game trip, which ends Sunday in Washington. Pittsburgh is 10-3-1 in its last 14 games, and 7-1-1 since Bylsma took over as interim coach on Feb. 15.
"Every game we're working hard and giving ourselves a chance," Crosby said. "There's some games where you work hard and you don't always get the breaks and things like that. We're working hard and we're getting rewarded, so we want to keep going."
Notes: Panthers D Nick Boynton, sent home from the team's last road trip for disciplinary reasons, returned to the club Thursday, but didn't play. ... Penguins D Sergei Gonchar missed the game to fly back to Pittsburgh and be with his wife, who was going into labor.