Carter Verhaeghe had two goals and an assist for the Panthers, Aleksander Barkov and Matthew Tkachuk each had a goal and two assists, and Montour also had two assists. Spencer Knight had 23 saves as Florida snapped a two-game skid.
Shane Pinto, Brady Tkachuk and Nick Holden scored for the Senators, who have lost two straight. Anton Forsberg stopped 53 shots.
''It was a good win,'' Panthers coach Paul Maurice said. ''They had won four of the past five coming in and are a quick-strike team. They are a team that has some high-end skill with some talented young players and if they catch you in open ice, they're going to to finish.''
After Montour gave the Panthers a 4-3 lead with his third of the season, Matthew Tkachuk sealed the win with an empty-netter with 14 seconds left.
Florida, which outshot Philadelphia 51-22 on Thursday night, had another big shooting night against the Senators.
Verhaeghe and Barkov scored about four minutes apart in the first period to give the Panthers a 2-0 lead as they outshot the Senators 26-4. Verhaeghe got the Panthers on the scoreboard at 7:59 and Barkov doubled the lead with a power-play goal with 8:06 left.
Pinto scored on the power play 37 seconds into the second and Brady Tkachuk beat Knight to tie it less than 3 minutes later.
''The shots (in the first) were pretty good for us and we want to play like that in every period,'' Barkov said. ''At the same time, we knew they would regroup and be better than that. And they were, right away. They got a goal on the first shift and got right back into the game.''
Ottawa appeared to take the lead when Tim Stutzle's shot deflected off Verhaeghe and past Knight at 5:26 of the second. However, Florida challenged for goalie interference and officials ruled Jake Sanderson impaired Knight and took the goal off the board.
Verhaeghe gave Florida the lead back with a blistering slap shot from the top of the right circle with 37 seconds left in the middle period.
In the third, Matthew Tkachuk scored in front of the net with 11:01 remaining, but Ottawa won its challenge that Florida was offside and that goal was erased as well.
Holden's goal with 8:04 to go in the third tied it 3-3.
`The first period is, well, it's our worst period of the year for sure,'' Ottawa coach D.J. Smith said. ''Just weren't ready when the game started. We battled back and we gave up a goal at the end of the second period, and then we give up a goal with three minutes to go. I mean, we kept battling but we've got to be better than that.''
The Tkachuk Brothers had a reunion on the ice on Saturday with Matthew meeting younger brother Brady for the first time as a member of the Panthers. The two are now in the same division for the first time since Calgary and Ottawa shared the North because of the pandemic in 2021. Matthew, who had two assists and a goal for the Panthers on Saturday, pulled his personal record against his brother to 8-8 in head-to-head meetings.
''I love playing against him,'' Matthew Tkachuk said before the game. ''One of the biggest honors for me is seeing him play in the NHL and seeing him have as much success as he's having. I'm so proud of him.''
NOTES: The Panthers scored their first power-play goal on home ice Saturday in their fourth home game. Florida had been 0 for 12 on the power play at home prior to Barkov's goal. ... Claude Giroux was facing Florida for the first time since it acquired him in a blockbuster trade with Philadelphia at the 2022 deadline. Giroux, who signed a three-year contract with Ottawa in the offseason, had three goals and 23 points in 18 regular-season games with the Panthers and three goals with eight points in 10 postseason games.
Senators: At Tampa Bay on Tuesday night.
Panthers: At Arizona on Tuesday night.
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