Alex Steeves scored twice for Toronto, and Justin Holl had a goal and an assist.
Tim Stutzle scored for the Senators, and Alex DeBrincat, who was acquired in a trade with the Chicago Blackhawks on July 7, had an assist.
Claude Giroux, who signed a three-year contract in free agency on July 13, did not have a point in his Senators debut.
It was the preseason opener for both teams, who were playing a split-squad doubleheader and also play later Saturday (7 p.m. ET).
Erik Kallgren made seven saves on eight shots for the Maple Leafs. He was replaced by Dylan Ferguson (nine saves) in the third period.
Cam Talbot made 10 saves on 13 shots in his Ottawa debut. He was acquired in a trade with the Minnesota Wild on July 12. Kevin Mandolese stopped all 11 shots he faced after replacing Talbot in the second period.
