He was the head football coach at the University of Hawaiʻi at Mānoa from 1988 to 1995, leading the Hawaii Rainbow Warriors to their first top 20 finish in 1992.
In 1971, he became head coach at River View High School in Warsaw, Ohio and led the team to its then-best season ever at 8–2.
[5] Wagner became an assistant coach at Hawaii in 1977 under Larry Price, then was promoted to defensive coordinator under Dick Tomey in 1983.
During most of Wagner's tenure at Hawaii, his offensive coordinator was Georgia Tech head coach Paul Johnson.
[11] Wagner served as the athletic director for Kamehameha Schools-Hawaii on the Big Island for ten years, from 2002 to 2012.