In her youth, Marjatta Moulin practiced tennis, swimming, skiing, and gymnastics, and thus did not settle on fencing as her sport of choice until 1951. A foil specialist, she won individual Finnish titles in that discipline eight times (1955, 1957, 1960, 1962, 1966-1968, and 1972) and over 20 team championships between 1954 and 1981. Her first major international appearance came at the 1953 World Championships, and she was the Nordic champion in 1959. She also competed in the 1960 Rome Olympics, where she was eliminated after losing four of her five bouts in round one. The following year, she earned a team Nordic championships title, and for many years thereafter she was active as a sports administrator and coach. Her sister, Aune Pärnänen, won three Finnish national titles in the 100m sprint in the 1940s.