At the 1956 Australian Championships, Devitt finished third in the 110-yard behind Henricks and Chapman, and fifth in the 220-yard behind Chapman to gain Olympic selection. After a ten-week national training camp at the Tobruk Pool in Townsville, Queensland, Devitt was named as the national captain for the 1956 Summer Olympics in Melbourne. Devitt's first event was the 100-metre freestyle, where he won his heat and then his semi-final to qualify in second place for the final, where he matched Henricks for the first 80 metres, before Henricks surged to claim gold. Chapman completed an Australian sweep by finishing third. For the 4×200-metre freestyle relay, Devitt had clocked the fourth fastest time at the Australian Championships. After swimming the fastest leg in the heats of the relay, he was selected along with Rose, Henricks and Kevin O'Halloran for the final. The Australians won the gold medal in a world record time, with Devitt clocking the fastest leg in the whole race.