The Capitals didn't give the Golden Knights much time or space early in the game. Even though they didn't score, the first period was arguably Washington's best period defensively in the series.
The Capitals blocked 15 shots, including four by defenseman John Carlson and two from forward Ovechkin, and won 13 of 18 face-offs. Ovechkin had three shots on goal, eight shot attempts and two hits.
"He set the tone with intensity, with physicality," Capitals coach Barry Trotz said of Ovechkin, the Washington captain.
The Golden Knights blamed themselves for being careless with the puck.
"You can live with the losses if you're just not getting the bounces, but the way we played isn't good enough for this time of year," Vegas forward Ryan Reaves said.
Ovechkin scored 1:10 into the second period to give Capitals a 1-0 lead. It was his 14th goal of the playoffs, tying him with John Druce for the Capitals record in a single postseason (Druce scored 14 in the 1990 playoffs).
Fleury stopped Carlson on a deflection, Kuznetsov from the high slot, and Carlson again from the low slot. The rebound came to Ovechkin, who scored on his backhand while falling over Vegas defenseman Brayden McNabb at the bottom of the left circle.
"I thought it was sort of the right thing in a playoff game, our first victory in the Final at home, that Alex would score the first goal," Trotz said. "I thought that was a little bit of poetic justice, if you will, for all the tough times."
Kuznetsov scored his 12th goal of the playoffs to give Washington a 2-0 lead at 12:50 of the second. T.J. Oshie blocked Shea Theodore's shot from the left point, and Beagle got the puck and moved it up to Kuznetsov, creating a 3-on-1 with Dmitry Orlov. Kuznetsov beat Fleury with a low blocker-side shot from the right circle.
Ovechkin, who was on the bench, was seen letting out a huge scream.
"It's just automatic," he said. "You just get excited."
Vegas got within 2-1 on Nosek's goal off a Holtby giveaway from behind the net at 3:29 of the third period, but Smith-Pelly gave Washington a 3-1 lead at 13:53.
Beagle took the puck from Theodore on the forecheck and passed to Smith-Pelly cutting to the net. He beat Fleury with a glove-side shot from the slot.
"I think we're getting stronger as this series goes on," Trotz said.