Lateef McMullan, Michael Harthun and Gary Winston each scored 13 points for Portland State (5-8, 3-3 Big Sky) while Aaron Moore had 12 points including an 8 for 9 performance from the free-throw line.
Portland State shot an even 50 percent from the field, making 26 of 52, and managed to recover from an early 7-0 deficit after the Lumberjacks hit their first three shots.
Northern Arizona (5-11, 2-4) led much of the first half but the Vikings used a 17-10 run over the final 9:05 to take a 34-32 lead at halftime. Portland State never trailed in the second half.
Gabe Rogers led the Lumberjacks with 17 points and four assists.