 Castleman served as the head football coach at the University of Colorado at Boulder in 1906 and 1907, compiling a record of 7–6–4.He was also the head basketball coach at Colorado in from 1906 to 1912, tallying a mark of 32–22, and the head baseball coach at the school from 1907 to 1913, amassing a record of 30–17.He was later the track coach at Ohio State University, where his team won the 1929 NCAA Men's Track and Field Championships.