Ned served as a high school baseball coach for more than 25 years. He is currently coaching baseball at McCluer North High School in Florissant. Mahon began coaching in 1974 at Hazelwood High School, where his team won the Missouri State Championship.

Between 1975 and 1980, Ned coached at Hazelwood West High. He then moved on to McCluer North, coaching the Stars from 1987-1995. There, his teams won six Suburban North Conference championships. Mahon received Coach of the Year honors in 1990, 1991, 1992 and 1994.