The Bulldogs (16-5, 8-2 West Coast) stormed ahead early and led by as many as 29 in the first half. Wiltjer had 23 points before the break, one more than the Broncos (7-15, 3-7) who trailed 46-22.
Gonzaga outrebounded Santa Clara 27-12 in the first half.
Domantas Sabonis had his 12th double-double of the season with 12 points and 17 rebounds. Kyle Dranginis scored 10 and Bryan Alberts made all three of his 3-point attempts for nine points. Gonzaga was 13 of 26 from long range.
Jared Brownridge led Santa Clara with 15 points, KJ Feagin scored 13 and Kai Healy added 10. The Broncos cut the deficit some in the second half but never threatened down the stretch.