Heikki Hasu competed successfully in both Nordic combined and cross-country skiing. Hasu made his international début at the 1948 Winter Olympics, where he was fourth in the 18 km skiing event and won gold in the Nordic combined. That year, he also won the Nordic combined at the Lahti Ski Games and he would record four more victories in Nordic combined at that tournament in 1949 and 1951-1953. At the 1950 World Championships, Hasu won the Nordic combined and won a silver as a member of Finnish cross-country relay team. At the 1952 Winter Olympics, Hasu won his second Olympic gold, this time in the cross-country relay, but in Nordic combined he had to settle for a silver medal behind Norwegian Simon Slåttvik. He also finished fourth in the 18 km cross-country race, losing a bronze medal by only four seconds to his fellow countryman Paavo Lonkila. In 1952 Hasu also became the first Finn and the last athlete who was successful in multiple Nordic skiing disciplines to be awarded the Holmenkollen Medal (shared with Stein Eriksen, Torbjørn Falkanger, and Nils Karlsson), although his only victory at Holmenkollen would come in 1953 in the Nordic combined. Hasu was selected as the Finnish Sportsman of the Year twice – in 1948 and 1950. After his competitive career Hasu was a farmer and served two terms in the Finnish Parliament (Eduskunta) from 1962-66 and 1967-70.