UC Santa Barbara held a 10-point lead at halftime, but Cal State Fullerton put up 44 in the second half to take the 67-62 win in the Thunderdome.
The Gauchos fall to 6-12 on the season and are 1-4 in Big West play. Fullerton improves to 7-11 and is now 3-2 in conference.
Melissa Zornig finished with a game-high 20 points after hitting four three-pointers in 39 minutes of play.
While the senior accounted for all of UCSB's shots from downtown, the Titans made a total of 10 as they were led by Tailer Butler's four.
Santa Barbara finished the first half with a 33-23 lead after outscoring Fullerton 14-2 in the paint.
With five lead changes, the Gauchos were able to take hold of a double digit lead after going on an 11-2 run starting at the 10:36 mark.
Mason sparked the run by sinking a jumper from the free throw line to put UCSB within one at 17-16.
Zornig then followed her fellow senior with her second three-ball of the night to give the Gauchos a lead with 9:59 left in the half.
Mason would go on to cap off the run with four straight points including a layup in transition.
During the play, Nicole Nesbit picked off a Titan pass and only had one defender to beat before making a quick bounce pass to the senior guard in the paint for easy finish.
Mason finished second in the game with 18 points.
Jemerigbe picked up one of her two assists on the play and finished the afternoon by tying a career-high in scoring with 11 points. Nesbit led the team with five assists.
The Gauchos maintained their lead until Butler sunk a three-pointer with 6:52 left in the game to make it 47-46.
UCSB momentarily retook the lead when Jemerigbe knocked down a shot from the right elbow. Zornig tried to solidify the advantage by burying a deep shot from the right corner, making the score 53-49.
However, Fullerton kept firing from three-point land and was back within one after Alex Thomas connected on a transition shot from the left wing.
After Mason responded with a jumper, the Titans put up six unanswered points and never gave up the lead.
UCSB finished under its season average in rebounds with 30. Mason led the team with eight boards, while Jasmine Ware and Zornig each pulled down six.
The Gauchos will hit the road next week with visits to UC Irvine (Jan. 30) and UC Davis (Feb.1). There will be audio broadcasts for both games featured on UCSBgauchos.com.