Steelheads rookie forward Austin Fyten scored the game-winning goal 18 minutes, 19 seconds into overtime Wednesday night in Stockton, Calif.
Fyten's power-play goal gave Idaho a 2-1 victory in Game 3 of the ECHL Western Conference Finals.
Stockton takes a 2-1 series lead into Game 4, which will be played at 8:30 p.m. Friday in California.
Steelheads forward Andrew Carroll scored the first goal of the game when he beat goalie Olivier Roy 11 minutes, 11 seconds into the second period. Carroll's third of the postseason gave Idaho the lead for the first time in the series.
The Steelheads maintained that lead until 2:51 into the third period, when Eric Hunter beat Idaho rookie goalie Josh Robinson, who turned away 41-of-42 shots. Roy stopped 40-of-42.
Idaho had to kill off three penalties in the scoreless first period, and Stockton had another power-play opportunity before Stockton was whistled in the second period.
Forward Austin Smith tallied assists on each of Idaho's goals. Gord Baldwin and Ben Ondrus also notched assists for Idaho, which improved to 5-2 in postseason overtime games this year.