"I'm proud to announce that for the 2021-22 season I'll be playing with the Boston Celtics," Schroder wrote on Instagram. "This is one of the best franchises in NBA history and it will be [an honor] to put on the green and white and do what I love! I'm going out there every night and leaving it all on the floor for the city!!"
The 27-year-old Schroder was the last significant unrestricted free agent left on the market. The former first-round draft pick turned down a lucrative extension from the Lakers in the middle of last season -- worth more than $80 million -- to pursue a larger deal this summer.
Schroder replaces former Celtics point guard Kemba Walker, who was traded to the Oklahoma City Thunder in June. Walker later agreed to a contract buyout with the Thunder, clearing the way for him to join his hometown New York Knicks.
The Lakers traded Danny Green and a 2020 first-round draft pick to the Thunder in exchange for Schroder in November. In his lone season in Los Angeles, Schroder averaged 15.4 points and 5.8 assists over 61 games.
The Celtics are coming off a disappointing season in which they finished seventh in the Eastern Conference and lost in five games to the Brooklyn Nets during the first round of the playoffs.