Kelly Olynyk provided a double-double 15 points and 11 rebounds for the Bulldogs (29-2, 16-0 WCC), who wrapped up their 10th outright WCC title.
With its 12th consecutive win, Gonzaga is likely to emerge Monday with its first-ever national No. 1 ranking.
The Pilots (11-20, 4-12), meanwhile, dropped their 20th straight to the Bulldogs.
Derrick Rodgers led Portland with 10 points.