Jennings had 14 points and four steals in 31 minutes and Andre Drummond and Josh Smith added 15 points each to help the Pistons keep the Celtics and their first-year coach winless with an 87-77 victory.
"I'm ready to play now," Jennings said after missing the team's first two games and most of the preseason with a jaw fracture related to a wisdom tooth.
The Pistons (2-1) trailed 65-63 early in the fourth quarter but went on a 10-0 run to take the lead for good and win their second home game in as many tries. Drummond added 12 rebounds for his second straight double-double and Greg Monroe grabbed 10.
Jennings had two steals after the Celtics cut the lead to 79-77 with less than 2 minutes to play. He got the first steal to Rodney Stuckey, who was fouled and made two free throws to give the Pistons some breathing room. Detroit held Boston scoreless the rest of the way.
"It was good to see him out there and the effect he can have on the team," coach Maurice Cheeks said of Jennings. "He brings a little electricity to a game."
"We had stretches where we played well defensively," Olynyk said, "but there were too many times when they got away with a couple of big runs."
The Pistons outscored the Celtics 10-5 in the last 5 minutes of the first half and took a 45-35 lead. Boston made just five field goals in the second quarter and had that many turnovers.
The Celtics finished with 24 turnovers and Detroit had 21. Cheeks said turnovers -- the Pistons had 60 in their first three games -- remain a concern.
"Our defense is usually pretty good but when we have turnovers, it's tough to get back and defend," he said. "It's something we have to keep working on."
Detroit was much more effective on the glass, where it outrebounded Boston 44-37.
"We had our opportunities," Stevens said. "They pounded us in the paint all night and that really hurt us."
Detroit outscored Boston 54-38 down low.
Jennings, who came to Detroit during the offseason in a sign-and-trade deal with Milwaukee, wore a facemask that covered his chin. He took the mask off in the fourth quarter because it was uncomfortable. His jaw remains closed with a series of bands while the fracture heals.
"I'm not used to playing with something on my face so it was my decision to take it off," he said.
He fell to the court after colliding with Brandon Bass in the final seconds of the first half but showed no ill effects when he returned for the third quarter.
Crawford was assessed a technical foul by referee Sean Corbin midway through the fourth quarter. ... Detroit F Charlie Villanueva (left shoulder) missed his third straight game. ... Detroit wore navy jerseys with "Motor City" in place of the team's name. The salute to the region's automotive heritage will be worn nine more times this season.