Born in Butte, Montana, Petrino grew up in Helena and graduated from its Capital High School.

[1][2] Recruited by the University of Montana in Missoula,[3] Petrino stayed in Helena and attended Carroll College.

He played quarterback for the Fighting Saints, where his father, Bob Petrino Sr., was the head coach from 1971 to 1998.

After more than two decades back in the Football Bowl Subdivision (FBS), Idaho returned to the Big Sky Conference in FCS in 2018.

Petrino's record at Idaho was 34–66 (.340), the nine seasons and 66 losses are the most by a head coach in program history.