In a match that took nearly three hours, UCLA struggled past Pepperdine, 5-15, 15-13, 15-13, 14-16, 15-8, in the Reebok volleyball tournament Friday night before 2,120 at Pauley Pavilion.
Fifth-ranked UCLA will meet USC tonight at 8 p.m. in the championship match.
USC beat Penn State, 15-7, 15-10, 15-13.
Pepperdine will play Penn State in the consolation match at 6 p.m.
In the opening game, the top-ranked Trojans had an easier time than was expected in beating the second-ranked Nittany Lions.
After winning the first game with ease, the Trojans seemingly lulled themselves to sleep for much of the rest of the match.
A surge by Penn State in the second game woke up USC, and the Trojans had to come from behind in the final game for the win.
"I was pleased with our comeback in the third game," USC Coach Bob Yoder said. "We played great for a game-and-a-half, both on offense and defense, but then we started to cruise.
"We were still playing good offensively, but we weren't playing any defense. That gave them confidence. We let them back into that game (second game) then they jumped on us in the third. But I'm glad we got into that situation and showed we could come back."
Penn State was without Chris Chase, a 6-foot 10-inch middle blocker. The two-time All-American has a leg injury.
USC had a big edge in serving, with five service aces to none for Penn State. Jen-Kai Liu led the Trojans with 21 kills, Tom Duke had 20 and Bryan Ivie had 19.
For the Nittany Lions, David Bittner had 21 kills, and Mike Hogan, John Wasielewski and Robert Pierce each had 13.