The Celtics finished with a record of 50–32, a 12 win drop off from the previous season.
They finished 1st in the Atlantic Division and 4th in the Eastern Conference.
In the playoffs, the Celtics defeated the Miami Heat in five games in the First Round, then defeated the top-seeded Cleveland Cavaliers (in a rematch of the 2008 Conference semifinals) again in six games in the Semifinals, and finally, defeated the second-seeded Orlando Magic (the runner-up of last year's Finals as well as the team that defeated the Celtics in last season's Conference semifinals in seven games) in six games in the conference finals to advance to the NBA Finals for the twenty-first time in franchise history.
The Celtics made it back to the NBA Finals after a one-year hiatus and played against the defending NBA champion and their rival, the Los Angeles Lakers for the 12th time.
In a rematch of the 2008 NBA Finals, in which the Celtics defeated the Lakers in six games to capture their seventeenth championship, the Celtics were defeated this time by the Lakers in seven games.