Cross-country skier Sixten Jernberg made his Olympic debut at the 1956 Olympic Games in Cortina d’Ampezzo. He earned silver medals in both of his first two races, the 30km and the 15km. Then he won the 50km by an impressive 78 seconds. Two days later, Jernberg skied the anchor leg in the 4x10km relay and secured bronze medals for Sweden's team.
At the next Winter Games, in Squaw Valley in 1960, Jernberg opened with a 13-second victory in the 30km race. He added a silver medal in the 15km, missing another gold by only 3.1 seconds, and then placed fourth in the relay and fifth in the 50km.
Four years later, Jernberg got off to a slow start (by his standards) at the 1964 Games in Innsbruck, finishing fifth in the 30km race and third in the 15km. In the 50km race, Jernberg started the course next to last, just as he had when he won the same race in 1956. Evidently, this was his lucky position because he won again in 1964, this time by 65.6 seconds. On 8 February 1964, two days after his 35th birthday, Jernberg competed in his last Olympic race, the 4x10km relay. Skiing the second leg, he helped Sweden score a close victory over Finland.