Josh Cremasco got the rebound for Warwick to score a two pointer and a free throw for a 70-66 lead.
DJ Cremasco and James Legan added three pointers but Saints again fought back to only trail 78-77 at three-quarter time.
There was no score in the first two minutes of the last quarter before DJ Cremasco and Legan scored three pointers, James Kuon did a slam dunk for Warwick for a 86-77 lead with seven minutes to go.
Warwick maintained the lead but Saints twice got to within three pointer of the Wildcats.
With 39 seconds to go, Ashley Williamson landed a free shot to put Warwick up 95-91. Josh converted a free throw, DJ scored a three pointer with five seconds to go and it was Warwick home 99-91.
Kuon put a lot of the credit for the Warwick win at the feet of DJ Cremasco.
"DJ came out in the first half and gave us a lift which got us over the hump,” Kuon said after the game.
In the other A-grade semi, USQ narrowly beat Runnin Rebels,
Warwick has secured home ground advantage for the grand final next Saturday. Saints and USQ will play this Sunday in the preliminary final with the winner to play Warwick next weekend.