The 2020 Tacoma Defiance season was the club's sixth year of existence, formerly as Seattle Sounders FC 2, and their sixth season in the USL Championship, the second tier of the United States Soccer Pyramid.

Note: Flags indicate national team as defined under FIFA eligibility rules.

Source: USL Championship Win Draw Loss Upcoming fixture Due to their ownership by a higher division professional club (Seattle Sounders FC), Tacoma is one of 15 teams expressly forbidden from entering the Cup competition.

For transfers in, dates listed are when Tacoma Defiance officially signed the players to the roster.

For transfers out, dates listed are when Defiance officially removed the players from its roster, not when they signed with another club.