Stephenson finished with 12 points, 10 rebounds and 10 assists, his second triple-double in two games against the Celtics this season.
Pacers forward Danny Granger, playing just his second game this season after sitting out with a strained left calf, scored 12 points and made four of five three-pointers off the bench.
Indiana (22-5) won their second game in a row after losing three of five.
The blowout followed a 114-81 victory over the Houston Rockets on Friday.
Avery Bradley scored 13 points and Jeff Green and Courtney Lee scored 11 points apiece for the Celtics (12-17), who entered the game tied for the Atlantic Division lead.
- - -
Raptors 104, Thunder 98
Kyle Lowry scored 22 points in leading the Toronto Raptors to a surprise victory over the Oklahoma City Thunder.
The loss ended the Thunder's 13-game home win streak to start the season. It also put a halt to a nine game overall win streak.
With 4:34 left in the fourth quarter, Raptors (11-14) guard John Salmons tied the game with a jumper. Center Jonas Valanciunas and guard Kyle Lowry scored five straight and the Thunder found themselves trailing 98-93 with 2:20 remaining.
Westbrook paced the Thunder (22-5) with 27 points, nine rebounds and five assists. Durant scored 24 points on 5-for-16 shooting as the Thunder fell one night after beating West rival San Antonio.
- - -
Clippers 120, Timberwolves 116 (Overtime)
Chris Paul hit five free throws in the final 20 seconds of overtime as the Los Angeles Clippers rallied to a victory over the Minnesota Timberwolves.
Paul, who finished with 19 points and 13 assists, also forced a turnover by Minnesota guard Kevin Martin that led to the extra session.
Forward Blake Griffin led Los Angeles with 32 points. He also had 10 rebounds and four steals before fouling out in overtime for the Clippers (20-9).
Minnesota (13-15) forward Kevin Love produced game highs with 45 points and 19 boards. Center Nikola Pekovic added a career-high 34 points and 14 rebounds for the Timberwolves, who lost to the Clippers for the eighth consecutive time.
The Clippers forced overtime on a Paul steal from Martin, leading to a dunk by Jamal Crawford with 7.7 seconds left. Pekovic missed two shots that prevented Minnesota from winning in regulation.