"I'm proud of the resilience of these young men," Cal coach Jack Clark said.
The Cougars clawed back from a 21-7 second-half deficit to thrill a blue-and-white dominated crowd of 11,000 at Rio Tinto Stadium during the closing minutes.
But BYU (15-1) ultimately had no answer for the power and athleticism of Cal (27-0), and the Golden Bears ended their season the same way they did last year outmuscling the Cougars and taking the crown.
"They played a smart game of rugby," BYU coach David Smyth said. "They came in with a very definite game plan, and that was to starve us of the ball to keep it with their big fellas and just to keep churning up the field. And they were very good at it, very patient."
Patience was key during the first 23 minutes, as the scoreboard remained blank and defense was prized.
However, the Golden Bears broke through at the 23:10 mark, when captain Derek Asbun pushed through for a gutsy try near the left side of the goal to give Cal a 5-0 lead.
James Bailes then drilled a penalty kick from dead center, extending the Golden Bears' advantage to 10-0 with five minutes remaining in the first half.
But BYU showed resolve. Quickly marching down the left sideline, the Cougars mounted an extended power attack that peaked with Apenisa Malani's try. A conversion by Shaun Davies followed, pulling BYU within 10-7.
Less than two minutes later, though, Cal struck again. Bailes dropped in another penalty kick, giving the Golden Bears a 13-7 lead just before the half expired.
"We couldn't get in there and turn the ball over enough," Smyth said.
Penalties plagued the Cougars after the break. Two flags helped Cal maintain pressure, and the Golden Bears jumped ahead 16-7 after a penalty kick 10 minutes into the second half.
By the time Cal's Seamus Kelly broke free along the left sideline for an untouched try midway through the final period, it was 21-7 Golden Bears, and Cal's continued dominance over BYU was clear.
"I feel like we gave all, and I feel like we played a better team," Malani said.
Despite the defeat, finishing one win away from the national championship and pouring out sweat in front of a devoted audience that attempted to carry the Cougars with echoing "BYU" chants left a lasting impression on Malani.
"I'm so grateful for the supporters today," he said.
R The Golden Bears downed BYU 21-14 to win the College Premier Division rugby national championship for the fifth time in six seasons.