The Celtics can close out the Eastern Conference series Sunday in Indianapolis.
Irving also had 10 assists and five rebounds.
Tyreke Evans matched his career playoff high with 19 points for the Pacers. Bojan Bogdanovic had 15, not enough to prevent Indiana from losing its sixth straight to Boston in the regular season and playoff.
Indiana desperately needed a win to avoid facing its second sweep in three years, but Boston started fast and closed it with a 10-4 spurt late in the fourth quarter.
And once again, Boston’s defense turned the game by allowing just 12 points in the third quarter.
It’s been that kind of series for Indiana, which erased a 15-point first half deficit to take a 61-59 halftime lead. Myles Turner opened the third with a 3-pointer to make it a five-point game.
But Boston charged back with eight straight points to retake the lead, closed the quarter on a 9-2 run to make it 80-73 and pulled away late.
The Celtics took control quickly by going 8 of 10 on 3s in the first quarter to build a 37-22 lead.
Evans finally got the Pacers righted with 12 second-quarter points including bookend 3s to start and finish the 17-3 spurt that allowed Indiana to tie it at 52. The Pacers closed the half on a 9-2 run to take the lead.