Kalevi Hämäläinen made his international début at the 1956 Olympic Winter Games, where he was 20th in the 30 km. At the 1958 World Championships Hämäläinen took part in every available cross-country event and won gold in the 50 km, bronze in the relay, was seventh over 50 km and tenth at 15 km. At the 1960 Olympics he placed 12th in the 30 km, before winning gold in the 50 km. At the 1962 World Championships Hämäläinen won a bronze in 50 km, his last major tournament medal. He also competed at the 1964 Winter Olympics, where he was 16th at 50 km and also trained to compete at the 1968 Winter Olympics, but was not selected for the Finnish team. In 1966 Hämäläinen won his only victory at Lahti by winning the 50 km. By profession he was a forester.