Originally a successful steeplechase runner, Cierpinski entered his first marathon in 1974. He was little known when he ran his fifth marathon at the 1976 Olympic Games in Montreal. More than three-fourths of the 26-mile, 385-yard (42.195 km) race had been run when he took the lead from the favourite, defending champion Frank Shorter of the United States, and Cierpinski won in 2:09:55, two minutes faster than Shorter's Olympic record.

Cierpinski returned to run in the marathon at the 1980 Olympics in Moscow, where he won an extremely close race in 2:11:03.