enrolled at the University of Michigan in 1967, having been recruited by Michigan Wolverines football coach Bump Elliott. He played on both offense and defense for Michigan's all-freshman football team in 1967. As a freshman, he was also the training adversary for NCAA heavyweight wrestling champion Dave Porter. 1968 season As a sophomore, Dierdorf started nine of ten games at the right offensive tackle position for the 1968 Michigan football team that compiled an 8-2 record in Bump Elliott's final season as head coach. Elliott called Dierdorf "without a doubt" his "most active and talented offensive lineman". In Michigan's victory over Wisconsin, Dierdorf played a key role blocking for Ron Johnson as Johnson set an NCAA record with 347 rushing yards and a Big Ten record with five rushing touchdowns. Dierdorf was credited with opening gaping holes on three of Johnson's touchdown runs. Michigan assistant coach Tony Mason said, "He just blew people out of Johnson's way like they weren't even there." Dierdorf received second-team All-Big Ten honors from the Associated Press (AP) in 1968. Dierdorf sustained a knee injury on the first play of the 1968 Michigan–Ohio State game, and his ability to return to the team remained doubtful until the start of the 1969 season. 1969 season In 1969, Bo Schembechler took over as Michigan's coach and led the 1969 team to a Big Ten Conference championship and a No. 9 ranking in the final AP Poll. Dierdorf started seven games at right offensive tackle and one at left offensive tackle. At six feet, four inches, and 255 pounds, he was the team's strong tackle, switching from one side of the line to the other, so that he could lead the play no matter which way it went. Michigan's 1969 season culminated with a 24–12 upset victory over No. 1 Ohio State. For his performance in the Ohio State game, Dierdorf received the UPI's Lineman of the Week award. Dierdorf was selected by both the Associated Press (AP) and United Press International (UPI) as a first-team player on the 1969 All-Big Ten Conference football team. He also received second-team All-American honors from the Central Press. 1970 season As a senior, Dierdorf started nine games at right tackle and one at left tackle for the 1970 Michigan team that compiled a 9–1 record. At an October 1970 press luncheon, coach Schembechler opined that Dierdorf was "as good as any