Lion City Sailors were the defending champions, having won their third Singapore Premier League title in the previous season.
Note: Flags indicate national team as has been defined under FIFA eligibility rules.
Note 1: Marko Kraljević was subsequently appointed as the Head, Youth for Hougang United.
Singapore Premier League clubs can sign a maximum of four foreign players in the 2021 season, up from three as compared to 2019.
Albirex Niigata can sign up unlimited number of Singaporean players for the new season.