A recipient of France's Legion of Honour and Croix de Guerre, and twice mentioned in despatches during the war, Watt was appointed an Officer of the Order of the British Empire in 1919. He left the military to pursue business interests in Australia, and was lauded for his generosity to other returned airmen. In 1921, at the age of forty-three, he died by accidental drowning at Bilgola Beach, New South Wales. He is commemorated by the Oswald Watt Gold Medal for outstanding achievement in Australian aviation, and the Oswald Watt Fund at the University of Sydney.