In 1955 D’Arcy Cowan was knighted for services to medicine, particularly in relation to his pioneering work in the field of tuberculosis (TB) prevention through the use of the BCG vaccine and the establishment of the National Association for the Prevention of TB.
Cowan was one of the founders of Bedford Industries, which continues to provide employment opportunities for disabled persons, with the main building named in his honour. He was also active in the South Australia Lawn Tennis Association and as an organiser of the Davis Cup competition.
The Sir D’Arcy Cowan Prize for Character and Service to the Boarding House is awarded annually at Speech Night.