Glen Davis added 15 points for the Celtics (6-1), who played their starters in the first and third quarters and the reserves in the second and fourth in their penultimate preseason game.
"I told them that they were only going to play 5 minutes in the third," Celtics coach Doc Rivers said, "but they came in at a timeout and asked, 'Can we finish this out and get the lead, and once we get the lead we'll come out?' It was good. They got stops and they played."
Danilo Galinari led New York (1-3) with 20 points on 6-of-11 shooting, Wilson Chandler added 17 points and Raymond Felton 16.
"They got into us in the third quarter," New York coach Mike D'Antoni said. "We were up 10 and they really got into us ... which is good. It's good that we can try to figure out what to do and try to get some scoring."
Knicks forward Amare Stoudemire, whose averaged 24.3 points in his first three games, rested Saturday, replaced in the starting lineup by guard Toney Douglas.
D'Antoni said the move was strictly precautionary, with the game opening a stretch of four in five days for the Knicks. Stoudemire, signed to a $100 million, five-year deal in the offseason, is likely to be in the lineup Sunday against Washington.
Jermaine O'Neal (hand) and Delonte West (lower back) also sat out Saturday for the Celtics, with West not making the trip after undergoing an MRI earlier in the day.