Center Ryan Watkins had 16 points and six rebounds in the first half as Boise State took a 44-31 lead at halftime against Idaho before a sellout crowd at CenturyLink Arena in Boise.
Guard Derrick Marks had 12 points for the Broncos (4-0).
Idaho senior Stephen Madison led the Vandals (3-3) with 12 first-half points and five rebounds.
Boise State attacked the paint against Idaho. The Broncos, the No. 1 scoring team in the country at 103.0 points per game, scored 28 points in the paint and added 16 points at the free-throw line in the first half. Boise State shot 60.9 percent from the field in the first half.
Boise State did not make a 3-pointer in the first half, missing all three attempts.
Idaho was 1-for-8 from 3-point range in the first half.
Boise State has won four straight games against Idaho.