The 2018 USL Cup playoffs was the postseason tournament following the 2018 United Soccer League regular season, the fourth since the league rebranded for the 2015 season, and second as a USSF Division II league. Including USL Pro history, it was the seventh postseason tournament. The tournament began on the weekend of October 20 and ended on November 8.

Sixteen teams (top 8 per conference) competed in the single elimination tournament. Teams were seeded one through eight in each conference. The conference semifinal winners played against each other in the Conference Championship, which served as the overall semifinals for the playoff. The winners of the Eastern and Western Conference Championship played for the USL Cup. The winner of the playoffs was to be crowned league champion.

FC Cincinnati clinched the USL regular-season title on September 26 and was the number one seed in the Eastern Conference.

The top 8 teams from each conference advance to the USL playoffs.

Championship Game MVP: Luke Spencer (LOU)