Hämäläinen, who started for the Sulkavan Urheilijat, won second place in the 18 km run at the Lahti Ski Games in February 1955 . At the 1956 Winter Olympics in Cortina d'Ampezzo , he finished 20th over 30 km. In early March 1956 he won the Lahti Ski Games over 18 km. At the Nordic World Ski Championships in Lahti in 1958 , he won the bronze medal with the relay and the gold medal over 30 km. He also achieved tenth place over 15 km and seventh place over 50 km. At the 1960 Winter Olympics in Squaw Valley , he won the gold medal over 50 km and also finished 12th over 30 km. Two years later he won the bronze medal over 50 km at the World Championships in Zakopane . In March 1963 he was eighth at the Holmenkollen Ski Festival over 50 km. At his last Olympic participation in Innsbruck in 1964 , he came in 16th place over 50 km. In March 1965 he won third place at the Lahti Ski Games and in March 1966 first place each over 50 km.