The Celtics jumped out first and led by as many as seven early but Portland pulled in front on Nicolas Batum's 3-pointer, which made it 18-15. Lillard's bank shot and free throw gave the Blazers a 38-27 lead midway through the second quarter.
Courtney Lee hit a 3-pointer and Garnett made a jumper to pull the Celtics to 41-39 with 1:31 left in the first half. Wesley Matthews answered with consecutive 3-pointers and the Blazers led 47-42 at the break.
Avery Bradley's fast-break dunk put the Celtics back in front 55-54 with 8:32 left in the third quarter, but the Blazers regained the lead and were ahead 71-67 going into the final period.
The game stayed close until Matthews made a 3-pointer to put Portland ahead 80-73 with 6:53 to go in the game. LaMarcus Aldridge extended the lead with his own 3 that made it 82-74.
"It was one of those 'my bad' games," Boston coach Doc Rivers said. "We just had so many of those 'My faults' where we lost sight of guys. We didn't finish any quarter right. It was a gettable game but give them credit, they made some big shots."
Jordan Crawford played 12 minutes but did not score in his second game for the Celtics. He was acquired in a deal with the Washington Wizards at the trade deadline on Thursday, so the Celtics were still working him in.
"He's a scorer, but we're going to ask him to do more than that," Boston coach Doc Rivers said.
Notes: Former Blazers President Larry Miller, now with Nike's Jordan brand, was at the game, as was former Portland Timbers coach John Spencer and Minnesota Lynx forward Maya Moore. ... The Celtics fell to 9-4 since losing Rajon Rondo to a season-ending knee injury. ... The victory snapped a six-game Portland losing streak in the series against Boston. ... It was Hickson's 19th consecutive game shooting 50 percent or better from the floor, an ongoing franchise record.