Cornel Vena studied Physical Education and Sport at the ICF Institute in Buçuresti, where he rowed with the eight. In 1953 he learned of the modern pentathlon and entered a qualifying tournament for the Romanian team, which consisted of swimming, running, and shooting, and to his surprise, won the event. He had to improve his swimming to compete internationally, but without much experience, he became an excellent fencer. Vena competed at the 1954 and 1955 World Championships, winning 22 bouts in the fencing phase of the modern pentathlon. At the 1956 Olympics, he won 29 of 35 bouts in fencing, scoring 1,111 points. Although records are not fully complete for the early years, this is the best known performance in Olympic modern pentathlon fencing, winning 82.9% of his bouts, and the highest score ever awarded in fencing in the Olympic modern pentathlon.