The Cougars outlasted San Francisco in the West Coast Conference Tournament semifinals, 79-77 in overtime.
Tyler Haws led BYU with 24 points, going 14 for 14 from the free throw line. Kyle Collinsworth added 18 points and 12 rebounds, while Anson Winder scored 15 points.
BYU advances to the WCC Tournament championship game for the first time in its three years in the league, and will take on Gonzaga Tuesday night.
While the Cougars (23-10) have probably locked up a spot in the NCAA Tournament, a win over Gonzaga would guarantee a bid.
BYU had a 64-56 lead with under six minutes to play in regulation, but BYU went scoreless in the final 6:15, and the Dons went on an 8-0 run to send the game in overtime.
In the extra period, Haws scored eight points, including making all six of his free throw attempts.
BYU and Gonzaga, which split their regular season meetings with each team winning on its home floor, will play for the WCC Tournament championship at 7:00 mountain time in Las Vegas.