Kim Mi-Seop was a member of the Korea Armed Forces and competed in the modern pentathlon at international competitions. In 1994 Kim won silver in the team event, along with an individual bronze at the Asian Games in Hiroshima. Two years later he represented South Korea at the Atlanta Olympics, placing 11th overall, with his best performance coming in the swimming element, where he finished second. In 2002 Kim then won gold in the individual, relay, and team events at the Asian Games in Busan. He later moved to the United States, living in Texas.