With the win, Saint Mary's improves to 17-7, 9-3 West Coast Conference, while Portland drops to 10-16, 5-8 WCC.
"This northwest trip is always difficult and to pick up a split is a positive," said head coach Paul Thomas. "As we move to the last couple weeks, each and every game is a battle of wills and toughness. We showed both tonight."
The Gaels built a 12 point lead in the first half, and led by 11 in the second half before foul trouble and injuries forced the SMC bench to step up.
For the Gaels, Danielle Mauldin led the way with 13 points and 10 rebounds, while Kate Gaze added 12 points and three assists. Jackie Nared was on her way to a double-double but left the game with 16 minutes left in the second half. Nared finished with eight points and nine rebounds in just 21 minutes of action.
Portland was led by Kari Luttinen with 13 points.
Saint Mary's led 31-20 with 13:36 remaining when Portland went on a run. The Pilots came back within 31-28, before the Gaels quickly extended the lead back to double-digits at 38-28 after Amanda Arter's big three-pointer with 7:16 remaining.
Portland came all the way back to tie it up at 40-40 with 3:55 remaining. Portland would never take the lead however, as the Gaels applied strong defense.
With the score tied up at 43-43, Mauldin made 1-fo-2 free-throws and Kate Gaze scored a key basket in traffic to push SMC up 46-43 with 1:01 left.
SMC would force a missed three-pointer and a the Gaels were fouled on the rebound as Gaze calmly sank two free-throws which put SMC up by five and locked up the win with 16 seconds left.
Saint Mary's shot 40 percent while holding UP to 27.8 percent from the field. The Gaels outrebounded UP 37-33. Saint Mary's had to overcome a cold night from three-point range as Arter's three was the only successful one of the night in 16 attempts.
Lauren Nicholson played 18 minutes off the bench while Andrea Bailey added four points and three rebounds in 11 minutes.
Saint Mary's is back in action on Thursday when it takes on the Toreros in San Diego at 7:00 p.m.