The incident occurred late in the fourth quarter, when Garnett went out to challenge a 3-point shot and hit Frye in the groin area as he reached back. Garnett wasn't looking as he reached back, but Frye grimaced as he went down and jumped up, going face to face with Garnett.
Players from both teams had to be separated and Garnett was hit with two technical fouls. Frye also got a technical, as did Boston guard Nate Robinson.
The technicals were called after a long video review by the officials.
Earlier in the game, Celtics coach Doc Rivers was ejected for arguing with an official in the second quarter.
With the Celtics trailing 40-25, Rivers was ejected late in the quarter after arguing with referee Steve Javie during a timeout. Rivers was hit with one technical foul and kept arguing with Javie, pointing to the official and his head as he yelled across the court.
Rivers got in a few more choice words before finally walking off the court.
A few minutes later, Celtics forward Glen Davis left with a strained right hamstring and missed the second half.
The Celtics got center Shaquille O'Neal back after he missed three games with a sore hip, then lost Davis for the second half Friday night.
Davis, averaging 12.3 points and 5.4 rebounds as a reserve, had two points and two rebounds in the first half. Boston struggled throughout the half and was trailing 49-35 when he went out.
Information from The Associated Press was used in this report.