Washington opened the scoring 2:39 into the contest on their first shot of the game when Dillon fired a one-timer from the point in past Tokarski.
Ovechkin gave Washington a 2-0 lead with the 727th goal of his career when his cross-ice attempt bounced off Rasmus Dahlin in front of the net and in with 8:21 remaining in the first.
Buffalo got on the board with 1:34 left in the opening period on Jokiharju's wrist shot from the left wing that found twine.
The two clubs started the second period 4-on-4. The Capitals regained their two-goal advantage 28 seconds into the second period when Schultz's slap shot from the point, fired quickly after a faceoff win by Washington, beat Tokarski.
The Sabres made it a one-goal game with 9:52 remaining in the second period. Rasmus Asplund won a battle behind the Washington net and dished the puck to Mittelstadt in front, who put on a deke and roofed a shot over Vanecek.
Vrana made it 4-2 at the 9:48 mark of the third.
With 3:13 left, Tom Wilson thought he extended the lead to three goals when he potted a rebound, but Buffalo challenged the play and it was deemed to have been offside. The goal was taken off the board.
Thompson made it a one-goal game when he redirected in a low point shot by Rasmus Ristolainen with 1:20 remaining in regulation.
Thompson has goals in back-to-back games and is on a three-game point streak (2+1). He has four points over his last five games (3+1).