But trailing by four, Henderson hit a 3-point with 1:01 left. After Avery Bradley missed an open jumper, Sessions came free off a screen and knocked down an 18-footer to give the Bobcats the lead with 25.7 seconds remaining.
The Celtics called timeout but Garnett missed an 18-footer from the left wing. Mullens grabbed his 18th rebound and the Walker made a pair of key free throws to give the Bobcats a three-point lead with 14.8 seconds left.
Boston set up an inbounds play and Pierce got an open look but missed. He grabbed his own rebound and dished out to the wing for Bradley, but he missed a 3 as time expired.
Despite coming off a triple-overtime win against Denver on Sunday night, the Celtics came out of the gates strong with solid shooting and aggressive defense to take a 48-42 lead at halftime.
As he'd planned to do before the game, coach Doc Rivers went deep into his bench in the first half with 10 players seeing at least 10 minutes of action.
The Bobcats battled back in the third quarter behind 12 points from Mullens to take a 75-72 lead into the fourth. Mullens, who scored Charlotte's first 10 points of the game, did most of his damage from outside, knocking down 3-pointers and turnaround jumpers showing great touch for a big man.
Celtics reserve guard Leandro Barbosa injured his left knee late in the third quarter and did not return. He was carried to the locker room by a trainer and teammate after collapsing near the baseline.
CLIPPERS 107, SIXERS 90: In Philadelphia, Chris Paul had 21 points and 11 assists and Blake Griffin scored 20 as Los Angeles cruised to a victory.
Jamal Crawford also scored 20 points and Matt Barnes had 11 for the Pacific Division-leading Clippers. Eric Bledsoe scored 10 points while DeAndre Jordan grabbed 10 rebounds.
The Clippers closed out their season-high eight-game road trip at 4-4, including consecutive wins at New York and Philadelphia.
Los Angeles won the finale with ease without guard Chauncey Billups and forward Caron Butler. Both players were nursing sore lower backs and were replaced in the starting lineup by Matt Barnes and Willie Green.
Nick Young led the Sixers with 29 points while Jrue Holiday, Evan Turner and Jeremy Pargo had 10 each. Spencer Hawes had 10 rebounds.
NETS 89, PACERS 84, OT: In Indianapolis, Brook Lopez scored 25 points and Brooklyn opened overtime on a 9-3 run to pull away from Indiana.
The Nets (30-22) ended a five-game losing streak at Bankers Life Fieldhouse and won for just the second time in games overall despite playing without injured guard Deron Williams.
Indiana (31-21) lost its second straight home game in overtime, the losses coming on the heels of a 15-game home winning streak. George Hill scored 22 points and Roy Hibbert added 12 on a night the Pacers shot just 34.4 percent from the field and All-Star Paul George finished with five points.
The Pacers appeared to swing the game with a 7-0 run that gave them a 76-72 lead with 1:38 left in regulation.
But Brooklyn scored the final four points to force overtime and started fast in the extra period to put away the game.