The Vikings led by four, 53-49 with 4:30 left in the game. Ty Egbert scored on a layup to halve the lead and Nate Sherwood halved it again by hitting the first of two free throws with 2:19 left.
Cameron Forte scored to push the Vikings' lead back to three, 55-52, but Sherwood connected on both free throws with 1:32 left. Portland State missed on a layup and a pair of 3-pointers as time wound down. Sarbaugh grabbed the rebound on Calaen Robinson's missed trey and immediately drew the foul from Isaiah Pineiro and converted the game-winning free throws.
Sherwood finished with 15 points to lead Idaho (12-9, 4-4 Big Sky).
Forte scored 20 points and grabbed a career-high 20 rebounds for Portland State (7-11, 3-4).