The Pacers won for the second time in nine games to pull even with Boston for the eighth and final playoff spot in the Eastern Conference.
Chandler Parsons led Dallas with 27 points. The Mavericks have a comfortable lead over Oklahoma City for the No. 7 seed in the West.
Indiana trailed 68-61 early in the third quarter, but pulled to 79-78 heading into the fourth.
The Pacers used an 8-2 flurry midway through the fourth to take a 97-91 lead.
After Dallas rallied to tie it 97, Roy Hibbert broke the tie two free throws and Miles followed with the 3-pointer. Parsons' 3 to force overtime in the closing seconds came up short.