The 2017 Seattle Sounders FC season was the club's ninth season in Major League Soccer, the United States' top-tier of professional soccer. The Sounders entered the 2017 season as the defending MLS Cup champions. The 2017 season is Brian Schmetzer's first full MLS season as head coach of the Sounders.
Numbers after plus-sign(+) denote appearances as a substitute.
|- |colspan="14"|Players who left the club during the season:
[S2] â S2 player