Triad defeated Mascoutah 1-0 in overtime in a Class 2A Mascoutah Regional semifinal game Wednesday.
Jaden Deatherage scored the only goal of the game on an assist by Grant Keller.
The Indians finished their season with a 18-7 record.
Reiss Naylor, goalkeeper for the Knights, had 10 saves in the shutout, his fourth of the season.
Triad (11-13-1) advances to play Columbia (23-0-2) in the Mascoutah regional championship game at 10 a.m. Saturday.