Thee signature of the 2.1m, 115kg power forward has come at a price.
Heading the other way to Minnesota are the Celtic forwards Al Jefferson, Ryan Gomes, the centre Theo Ratliff and guard Sebastian Telfair. Boston have also given up two first round draft picks.
Despite the addition of Garnett to their squad, a title is no formality for Boston who finished last season with a 24-58 record, the second worst in the NBA 24-58.
Given such poor form Garnett was initially apprehensive about joining the Celtics. However the team's capture of 32-year-old seven-time all star guard Ray Allen appeared to have helped him change his mind.
Paul Pierce, a 29-year-old forward boasting five all star apperances, is also currently on Boston's roster.
And while the signing of Garnett may have cost Boston most of its youth, they do now boast one of the most dangerous trios in the league.
"I am excited to become a Celtic," the 31-year-old said.
"It's wonderful to have the opportunity to play with players of the quality of Paul [Pierce] and Ray [Allen]."
"The Celtics have had a proud tradition and now I hope that we can add to the legacy."
Garnett has career averages of 20.4 points and 11.4 rebounds and has been named to the All-NBA defensive first or second teams eight times. He was the league's most valuable player in 2004.
Last season Garnett scored an average of 22.4 points a game and led the league in rebounding with a 12.8 average.
The Celtics have won 16 NBA championships but the last of those was in the 1985-86 season.