Brian Diemer ran his way to high school and Big Ten championship honors in high school at South Christian and at the University of Michigan, won a bronze medal in the 1984 Olympic Games in the 3,000-meter steeplechase and competed in two more Olympics before returning home to coach cross country with four national championships at Calvin College (now Calvin University).
He excelled in distance running and was the Class B state champion in the mile in 1978 and won the state titles in the two mile and mile in 1979 while running for South Christian.
At Michigan he was the Big Ten and NCAA Division I steeplechase champion as a senior, which helped propel him to the ’84 Olympics and his bronze medal finish.
He went on to win four TAC and USATF championships in 1988, ’89, ’90 and ’92, and in ’89 he won the Glenn Cunningham Award as the outstanding American male distance runner of the year. At the 1988 Olympics he was seventh in his semifinal heat of the steeplechase, and in 1992 as captain of the U.S. Olympic Track and Field Team, he qualified for the final and finished seventh.
Diemer was also a gold medalist in the steeplechase at the 1990 Goodwill Games, won the silver medal in the 1995 Pan American Games, and a silver medal in the U.S. Olympic Festival in 1995. He attempted to make his fourth Olympic team in the 1996 U.S. Olympic Track and Field Trials.
While coaching cross country at Calvin since 1986 with the men’s team and 2006 with the women’s team, as of 2019 he had led the men’s cross teams to 33 consecutive MIAA titles, 26 regional titles and the four national championships. Meanwhile, his women’s teams had won eight MIAA titles and eight regional titles.
He is the winningest MIAA cross country coach in history of the league competition. He has been named the Great Lakes Regional Men's Coach of the Year 18 times, the Great Lakes Regional Women's Coach of the Year four times and the NCAA Division III Men’s National Coach of the Year four times.
He is also active in community events as the charitable Brian Diemer Family of Races event has been presented annually for several years.