The 2020–21 1. FC Union Berlin season was the club's 56th season in existence and the second consecutive season in the top flight of German football, the Bundesliga. They also participated in the DFB-Pokal. The season covered the period from 1 July 2020 to 30 June 2021.
Note: Flags indicate national team as defined under FIFA eligibility rules; some limited exceptions apply. Players may hold more than one non-FIFA nationality.
^ abSince the winners of the 2020–21 DFB-Pokal, Borussia Dortmund, qualified for the Champions League based on league position, the Europa League group stage spot was passed to the sixth-placed team, and the Europa Conference League play-off round spot was passed to the seventh-placed team.