Rondo entered Friday's game against the Houston Rockets one assist shy of the 50-year-old mark and tied Cousy's 1959-60 total by setting up a 3-pointer by Paul Pierce 90 seconds in. With 8:45 to play in the first quarter, Rondo lobbed a perfect feed to Garnett from the top of the key, and the easy slam established the new mark.
The Celtics honored Rondo during the first timeout by acknowledging the record and the Garden crowd gave him with a standing ovation as the JumboTron displayed Cousy's No. 14 in the rafters.
With 10 assists on Friday, Rondo has 724 on the season with seven games to go. But he didn't feel much like focusing on one of the lone positives in Boston's 119-114 overtime loss.
"It's nice, but we lost, so I don't get to enjoy it too much," he said.
Last week, Rondo passed Rick Fox to establish a franchise single-season record for steals; he now has 181 on the season.
Rondo said the assists record means more to him than the steals mark. "Sharing the ball and trying to make my teammates a little better, that's what I pride myself on," he said.
Rondo finished Friday's game with 23 points, 10 assists, 5 rebounds and 5 steals over 48 minutes.