The Sounders entered the 2017 season as the defending MLS Cup champions.

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

Source: MLS Numbers after plus-sign(+) denote appearances as a substitute.

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

Only trades involving draft picks and executed after the start of 2017 MLS SuperDraft will be listed in the notes.