Tim Stutzle, Claude Giroux, Warren Foegele, Michael Amadio and Ridly Greig scored for the Senators (36-24-9), who have won four of their past five games and are 13-3-2 in their past 18. Jordan Spence and Tyler Kleven each had two assists, and Linus Ullmark made 12 saves.
Easton Cowan had a goal and an assist for the Maple Leafs (29-29-13), who have lost three straight (0-2-1). They lost 4-3 in overtime against the Carolina Hurricanes on Friday.
Starting for the second night in a row, Joseph Woll made 38 saves. Expected starter Anthony Stolarz took a puck to the throat in warmups and was taken to a hospital for precautionary imaging.
Stutzle gave Ottawa a 1-0 lead on the power play at 14:58 of the first period, beating Woll from the right face-off dot to the short side.
The Senators appeared to extend the lead twice before officially making it 2-0 at 9:09 of the second period. Drake Batherson had a goal waved off because Stutzle collided with Woll before the puck crossed the line, with Stutzle being called for interference at 6:07.
A point shot from Artem Zub was tipped by Greig past Woll at 8:26, but the goal was disallowed for a high stick.
Forty-three seconds later, Giroux made it 2-0 at the side of the net when he backhanded the rebound of his own tip attempt.
Foegele extended the lead to 3-0 at 17:53. After intercepting a clearing attempt by Philippe Myers, he scored from above the right circle with a shot that deflected off Maple Leafs defenseman Simon Benoit.
John Tavares responded for the Maple Leafs just 21 seconds later to make it 3-1 at 18:14, finishing a give-and-go with Cowan.
Cowan brought the Maple Leafs within 3-2 at 4:52 of the third period. He pounced on the rebound of a Benoit shot and scored from just outside the crease over a sprawling Ullmark.
Amadio put the Senators up 4-2 at 9:41, scoring on a tap-in from the left side after Spence’s shot banked off the end boards.
Greig restored the three-goal lead by making it 5-2 at 13:11. He took a pass from Dylan Cozens in the slot, went forehand to backhand and scored to the glove side.