Pekka Niemi won his only medal at the Finnish Championships, a silver, in 1935 in the 50 km. In 1935 he also won his first international race, the 50 km in Boden, Sweden. At the 1936 Winter Olympic Games Niemi won a bronze in the 18 km and then, three days later, was eighth at 50 km. But Niemi’s greatest success as a cross-country skier was at the 1937 World Championships, where he won a complete set of medals (gold in the 50 km, silver in the relay and bronze in the 18 km). In 1937 he also won the 50 km race in Ounasvaara, which he would also win in 1939 and 1941. In 1938 Niemi won the 50 km at the Holmenkollen Ski Festival and he was fourth at 50 km and tenth in the 18 km at the 1938 World Championships. Niemi took part in the 1939 World Championships, finishing fifth in the 50 km and sixth over 18 km, while in 1939 he also won a silver in the 50 km at the Lahti Ski Games. By profession Niemi was a district forest manager.