Erkki Mallenius took up boxing in 1945 and in 1946 won the Finnish junior lightweight title. In 1950, Mallenius won his only medal at the Finnish Championships, a welterweight bronze. In 1952, Mallenius won the Finnish Olympic light-welterweight trials and was selected for the Finnish Olympic team. At the 1952 Olympics, Mallenius fought only two matches, winning both of them by decision, but injured his hand in his second match against Belgian Jean Paternotte and the Finnish doctors wouldn’t allow him to box in this semi-final bout against Soviet Viktor Mednov, but this was enough for Mallenius to win a bronze medal. The hand injury sustained at the Olympics was so serious (he had broken a carpal bone), that Mallenius had to quit boxing. After finishing his boxing career, Mallenius worked as a boxing coach for a short while and then as a building contractor. Mallenius was selected to the Finnish Boxing Hall of Fame in 2008.