Kemba Walker shot just 4 of 20 from the field but hit a 3-pointer with about 2:30 left that pulled the Celtics to within 91-86.
Pritchard added a long 3-pointer with about a minute left that brought Boston to within 94-91, but Booker quickly responded with a contested 15-foot jumper and the Suns were able to hang on for the win.
The Suns jumped out to a 27-19 lead in the first quarter after the Celtics shot just 7 of 26 from the field. Boston tied the game late in the second, but Booker hit a 3-pointer with 0.8 seconds left to give Phoenix a 52-49 halftime advantage. Tatum led the Celtics with 12.
For the first time this season, the Suns hosted a small crowd at newly renovated Phoenix Suns Arena.