Luostarinen's centering pass went off a Capitals players stick and into the net, moving the Panthers to 9-0-1 with 19 points. The team's previous best 10-game start was in 1996-97, with a 7-0-3 record and 17 points.
Florida's Aleksander Barkov scored two goals, raising his career total to 188, tied with Olli Jokinen for the most in franchise history. Aaron Ekblad had a goal and assist, and Brandon Montour also scored for Florida.
The Panthers never gave up possession of the puck in overtime.
''I think that's the biggest thing you can do in overtime, just hold on to the puck and make them tired,'' Barkov said. ''It wasn't pretty today, but managing to get the win against a really good team, you're going to be happy with that, but then there's a lot of things we can work on.''
Spencer Knight stopped 25 shots after entering the game to start the second period. Sergei Bobrovsky stopped all 13 shots he faced before leaving after the first period with an upper-body injury. Bobrovsky is day-to-day, according to interim coach Andrew Brunette.
The Panthers have played three straight overtime games under Brunette, who took over last week after Joel Quenneville resigned as part of the fallout from the way Chicago handled allegations of sexual assault by a player against another coach in 2010.
''I'll take the points,'' Brunette said. ''I think I aged again tonight a little bit, but always take the win.''
Alex Ovechkin scored his 10th goal of the season and had two assists for Washington. Connor McMichael, Tom Wilson and Daniel Sprong also scored for the Capitals.
lya Samsonov stopped 15 of 18 shots before being replaced by Vitek Vanecek in the second period. Vanecek made 13 saves.
''The guys played hard, they never stopped playing,'' coach Peter Laviolette said. ''We found ourselves in a game where I thought we could have had the lead at times. We got to overtime and never really got possession of the puck. It's frustrating to not get the second point.''
McMichael tied the game with 13:04 left in regulation, capping a three-goal rally. The Caps scored two goals in the final 1:49 of the second period. Ovechkin got the 740th goal of his career, and Wilson redirected a shot by John Carlson to make it 4-3.
''We have to take a point any way we can, but in the first period we didn't play our game. After that we were pretty good,'' Ovechkin said.
Samsanov wasn't on the bench as the puck dropped. Vanecek played the first 1:45 of the game, facing no shots, and Samsanov came in after the first whistle. Samsonov was eventually replaced by Vanecek in the second period.
Florida plays host to Carolina on Saturday night, with the Hurricanes looking to tie the best start in NHL history at 10-0-0. The other teams who started a season with 10 consecutive victories were the 1993-94 Toronto Maple Leafs and the 2006-07 Buffalo Sabres. Florida started this season 8-0-0. ''Obviously, Florida is as good as they come. ... We know what we're getting there. That's going to be a tough one,'' Hurricanes coach Rod Brind'Amour said.
Florida's Chase Priskie - a Washington draft pick - made his NHL debut for the Panthers, becoming the first South Florida native to play for the team. Priskie grew up in Pembroke Pines, Florida, about a 15-minute drive from where the Panthers play. His first time at a Panthers game was when he was just a few weeks old; that's how big a fan of the team Priskie's father, Jeff, was. Jeff Priskie died in 2013. ''When I walk into this rink, all I can think about is my dad. I know he would be proud,'' Chase Priskie said.
NOTES: Knight became the 150th different goaltender Ovechkin has scored on in his career. ... Capitals forward Anthony Mantha left the game with an upper-body injury. ... It had been nearly two full years since Washington played at Florida, the last game between the teams before Thursday came on Nov. 7, 2019. ... The Capitals and Panthers play three times this season, all in November. Florida goes to Washington on Nov. 26 and Washington returns to Sunrise on Nov. 30. ... The Panthers are selling chili-cheese hot dogs - the King Dog - as part of their endorsement deal with Miami Hurricanes quarterback D'Eriq King. He's directing all proceeds go to the Hurricanes' offensive line, as part of his name-image-likeness deal with the Panthers.
Capitals: Host Philadelphia on Saturday.
Panthers: Host Carolina on Saturday.
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