The announcement occurred during the first timeout in Boston's game against the Clippers, with Garnett's former Boston coach, Doc Rivers, standing on the opposite sideline.
During a stoppage, the Celtics played a Garnett highlight video on the Jumbotron, accompanied by an audio clip from former Celtics coach Doc Rivers, saying, "I've never been around a player like Kevin".
"I'm honoured and thankful to have my number retired with the Celtics", Garnett said in a press release. He helped Boston to the National Basketball Association title in 2007-08 in his first season - winning Defensive Player of the Year honors along the way - and another Finals appearance in 2009-10, losing to the Los Angeles Lakers.
The first matchup between these two teams in November was an overtime thriller that just happened to be the first game with both Paul George and Kawhi Leonard on the court together for the Los Angeles Clippers.
In six seasons with the Celtics, Garnett averaged 15.7 points, 8.3 rebounds, and 2.7 assists in 31 minutes.
Following a stint with the Nets, Garnett returned to the Wolves during the 2014-15 season and retired in 2016. Garnett's former Celtics teammate Paul Pierce had his No. 34 raised to the rafters February 11, 2018. Garnett will be the 24th member of the Celtics organization to receive this honor.