UWA are RugbyWA's premier grade champions after beating Cottesloe 16-13 in Sunday's grand final at McGillivray Oval.
They led for almost the entire match, had a 16-0 first-half lead and survived a late Cottesloe surge to claim their second premiership in four years.
UWA had only won five of their first 10 regular season games and were outside the top four but went onto win five consecutive games at the tail end of the season to make the finals.
UWA scrum-half Ethan Carlisle was man of the match.
Coach Steve McFarland was delighted with the way his side played in the first half.
“We are pleased to have won it,” he said.
“We had a good lead in the first half where we applied pressure on Cottesloe and then that turned into scoreboard pressure.
“That certainly made it a challenge for them having to come from behind.”
Cottesloe coach Ian Fowler said his side made too many errors in the second half.
“We made a few mistakes at the end and were not able to get any continuity. I was happy at half-time and we had a 20-point breeze but we could not get it done today.”