But, moments later, UCI countered with a 16-0 spurt that turned into a 20-3 surge, to assume control and earn its fifth straight triumph.
The five-game winning streak is the longest since 2006 and the 'Eaters 5-3 start is the program's best in eight seasons.
"It's exciting," said Goodenbour, whose shift to a man-to-man defense after the Vikings' three-point run helped spark the turnaround. "I think we learned something about ourselves. Portland State is a very good team, probably the best we've played this year. They went on a great run and I did not know how we'd respond, because we haven't been in that situation. But I was proud of how we dug in. We were pretty relentless in the second half. I might have a basketball team, it looks like."
Senior point guard Jade Smith-Williams led the winners with 20 points, while junior Mikah Maly-Karros had 16 points and 13 rebounds.
Junior Kiara Belen had 13 points and, along with sophomore Jazmyne White and freshman Jacquelyn Marshall shared the team lead with three steals.
UCI shot 60% in the second half (18 for 30), including four of six from three-point range, to produce a season-high 53-point half.
But Goodenbour hesitated to call it a watershed win.
"Every game has been a breakthrough," Goodenbour said. "Every win has given us more confidence, given us a feeling that this is what we're supposed to do. It should be our expectation every time if we go out and play the way we're capable of playing, we can do that."
A testament to UCI's emerging depth, six players scored during the 16-0 run.
UCI was outrebounded, 30-16, before intermission, including 15 offensive boards for the Vikings. But UCI had a 19-10 advantage on the glass after the break and finished with just nine turnovers, to the Vikings' 20.
UCI, which wrapped up a stretch of four straight home games, takes nine days off for finals, before visiting Seattle on Dec. 13.
UC Irvine 75, Portland State 61
PSU – Samms 17, Valentine 3, Jones 20, VanBrocklin 12, Bishop 3, Wade 2, Brock 2, Egwuatu 2.
3-pt. Goals – Jones 4, Valentine 1, VanBrocklin 1, Bishop 1.
Fouled out – Valentine.
Technicals – None.
UCI – Maly-Karros 16, White 6, Belen 13, Marshall 8, Smith-Williams 20, McCalister 8, Cathey 4.
3-pt. Goals – Marshall 2, Smith-Williams 1, Belen 1, McCalister 1.
Fouled out – None.
Technicals – None.
Halftime: PSU, 24-22.