Paul George had 24 points for the Pacers, who staked the Sixers to a 15-6 lead before taking the lead and pulling away. George Hill scored 11 points, Ian Mahinmi had 10 and David West grabbed 12 rebounds.
Thaddeus Young had 23 points to lead the Sixers, who tied the Detroit Pistons for the sixth-longest losing streak in NBA history. The Pistons lost 21 straight bridging the 1979-80 and 1980-81 seasons.
The Cleveland Cavaliers set the NBA record for consecutive losses with 26, in the 2010-11 season.
The Sixers haven't won since Jan. 29 at Boston. Evan Turner, now with the Pacers, hit the game-winning shot in that 95-94 win by Philadelphia. Turner, traded to Indiana with Lavoy Allen on Feb. 20 for Danny Granger and a draft pick, had four points and seven rebounds against his former team on Monday.
Hollis Thompson and Tony Wroten each scored 17, Michael Carter-Williams had 15 points and 13 rebounds, and Henry Sims had nine points and 11 rebounds for the Sixers, who next host Chicago on Wednesday night.
Philadelphia built its 15-6 first-quarter lead by shooting 6 for 9 from the field, including 3 for 4 on 3-pointers, while the Pacers were 3 for 9 in the same stretch.
But Indiana closed the quarter on a 15-9 run to pull to 24-21. Mahinmi's rebound and dunk off a miss by Luis Scola miss gave the Pacers a 27-26 lead with 9:50 to play in the second quarter, their first lead since 2-0.
The second quarter saw seven lead changes and seven ties, the last on a jumper by Carter-Williams that tied the score at 48 with 2:11 to play.
Hill hit a 3-pointer to put Indiana up 51-48, George dunked, then hit a free throw after a technical on Byron Mullens for kicking the ball after he fouled Stephenson. Stephenson hit both free throws to give the Pacers a 56-48 lead. Indiana led 58-50 at halftime.
But the Pacers, who shot 13-for-21 in the second quarter, went cold in the third. Indiana was just 6-of-27 from the floor in the third quarter, giving Philadelphia a chance.
Young pulled the Sixers within 62-61 on a 3-pointer, then put them ahead 63-62 on a fadeaway jumper. West hit a free throw to tie the game, but a lane violation wiped out his second attempt.
Mahinmi broke the tie with two free throws with 3:39 to play in the third quarter.
Indiana's lead was 67-65 when George and Hill hit consecutive 3-pointers to extend the lead to eight. Young scored to make it 73-67, but West put back a miss by Hill to take a 75-67 lead into the fourth quarter.
The Sixers closed to 88-85, but Carter-Williams missed a potential tying 3-pointer with 2:15 remaining. Hill answered on the other end with a 3-pointer to give Indiana a 91-85 lead with 1:56 to play.
Hill then stole a Carter-Williams pass and Roy Hibbert completed a three-point play at the other end for a 94-85 advantage.