Mirja Hietamies’ first big accomplishment as a cross-country skier came in 1951, when she won a silver in the 10 km at Holmenkollen. At the 1952 Winter Olympics, she won a silver at 10 km, the first time women competed at the Olympics in cross-country skiing. At the 1954 World Championships Hietamies won bronze in the 10 km and silver in the relay and made her last international appearance at the 1956 Winter Olympics, where she won gold in the relay and was sixth over 10 km. Domestically Hietamies won Finnish titles in the 10 km in 1953 and 1956 and took bronze in 1952. In 1954 and 1955 she also won the 10 km race at both the Lahti Ski games and in Ounasvaara, being selected as Finland’s 1955 female athlete of the year. After her sporting career Hietamies worked as a member of the board with the Finnish Skiing Federation from 1965-67.