Jonathan Huberdeau scored, and Roberto Luongo made 22 saves for the Panthers (20-21-8), who had won three straight.
"We didn't play the way we wanted in the third," Huberdeau said. "We were up one goal and we let up. We gave up a lot of chances that we didn't in the first and the second."
Center Derick Brassard and forward Riley Sheahan, acquired by the Panthers in a trade with the Pittsburgh Penguins on Friday, did not play.
Nashville trailed 1-0 before Josi made it 1-1 at 5:29 of the third with a high wrist shot inside the far post from the left face-off circle.
Arvidsson made it 2-1 with a slap shot from the top of the right circle.
"I don't know if I fanned on it or it took a weird angle on him," Arvidsson said. "I just tried to rip it at the net as quick as I could and there was a stick in the way. Nice to see it go in."
Fiala made it 3-1 at 14:10 after Florida defenseman Mike Matheson misplayed a bouncing puck in the Panthers zone.
Arvidsson scored into an empty net with 1:56 remaining for the 4-1 final.
"It was building up, especially the second period," Forsberg said. "I thought we were playing pretty good in the second period too and obviously had a lot of chances. [Luongo] played great in net. We kept pushing and got rewarded in the third."
Huberdeau made it 1-0 on the power play at 15:15 of the second period with a wrist shot from the left circle. He became the fourth Panthers player, and first since Olli Jokinen in 2006-07, to reach 50 points before Florida's 50th game. He has 13 goals and 37 assists playing in all 49 games.