The Gaels stormed to a 36-19 halftime lead and did not let up while winning for the 25th time this season.
Dellavedova went 5-of-8 from 3-point range and Stephen Holt came off the bench to add 13 points. Saint Mary's is 25-5 for the season and 13-2 in West Coast Conference play.
Second-ranked Gonzaga has already clinched the league's regular-season title, having handed the Gael's their only two conference losses.
Pepperdine (12-16, 4-11) went 13-of-53 from the field and was only 4-of-20 from long range. The Waves were led by 12 points from Stacy Davis.