Boston’s Grant Williams finished with 27 points and shot 7-of-18 from three, tying the NBA record for most made three-pointers in a Game 7.
Jayson Tatum scored 23 points, shooting 5-of-9 from three, adding eight assists and six rebounds; Jaylen Brown finished with 19 points and eight rebounds.
Boston made 22 three-pointers on Sunday, shooting 40 percent (22-of-55) from beyond the arc.
The Celtics held the Bucks to 35.7% shooting from the field and 12.1% shooting from three. Giannis Antetokounmpo led Milwaukee with 25 points, 20 rebounds and nine assists. The former MVP shot just 38.5 from the field (10-of-26) and reached the free-throw line only six times.
Antetokounmpo’s 10 first-quarter points helped Milwaukee jump to a six-point lead after one quarter, 26-20. Boston would hold Antetokounmpo to only 15 points the rest of the game.
Boston outscored Milwaukee 28-17 in the second quarter, taking a slim 48-43 lead into halftime.
In the second half, the Celtics began to pull away, outscoring the Bucks by 10 in the third quarter to gain a 79-64 advantage heading into the fourth quarter.
The Bucks never got close in the fourth quarter as the Celtics continued to pour on the offensive pressure; Boston outscored the Bucks 30-17 in the final quarter.
Boston will open the Eastern Conference finals on the road against the Miami Heat Tuesday at 8:30 p.m. ET.
On Thursday, the Heat advanced to the Eastern Conference finals, knocking off the Philadelphia 76ers in six games.