He served as the head football coach at the South Dakota School of Mines—now known as South Dakota School of Mines and Technology—from 1929 to 1934 and Bethany College in Lindsborg, Kansas from 1938 to 1942 and again from 1946 to 1956, compiling a career college football coaching record of 70–104–4.
[10] Hahn stepped down as Bethany's head football coach in 1957 and was replaced by Hal Collins.
[11] He remained Bethany's athletics director until 1966, when he was succeeded by Keith Rasmussen, the school's head football and track coach.
Hahn continued as Bethany's head tennis and golf coach and as a professor of physical education.
[12] The Bethany College gymnasium was named the Hahn Physical Education Building in his honor.