He returned to Coraopolis, Pennsylvania, where he grew up, to begin his coaching career at the high school level, and then moved to the college ranks.
He was hired as head coach by his alma mater, Pitt in 1982, having previously been defensive coordinator under Jackie Sherrill, leading the team to a 25–18–3 record in four seasons before being fired.
Several of Fazio's defenses have been acclaimed as some of the best units in college football history, particularly the #2-ranked 1980 team which featured several players who went on to have successful careers in the NFL, including Rickey Jackson, Bill Maas, Carlton Williamson, and Hugh Green, who finished second in the 1980 Heisman Trophy balloting.
After Fazio's stint as head coach at Pitt, Lou Holtz then hired him to serve as the defensive coordinator at the University of Notre Dame.
He left the Vikings in 1999 and spent a year as the linebackers coach of the Washington Redskins before his hiring as the defensive coordinator of the Cleveland Browns in 2001.