Alan Williams, Jaime Serna and Kyle Boswell had nine points each for the Gauchos (16-9, 10-4 Big West), who moved into a second-place tie with Cal State Fullerton in the conference standings. The teams split two games this season.
Dylan Royer scored 14 points and David Hanson 13 for the Mustangs (15-14, 6-8).
Nunnally and Boswell scored seven points each during a 16-1 run over a 4:30 stretch of the first half. Nunnally’s 3-pointer gave UC Santa Barbara a 32-16 lead, and it maintained a comfortable cushion for almost the rest of the way.
Cal Poly got within 49-42 in the second half, but Nate Garth made a 3-pointer, and Johnson followed with a 3 and dunk as the Gauchos quickly regained control.