A third generation student at Prince Alfred College, Colin Gurner was a member of the First XVIII, First XI, and a Prefect. In 1936 he was a member of the school's Earl Roberts Cadet Rifle Team, which competed in the British Empire competition for school boys.
After graduating in medicine from the University of Adelaide in 1942, Colin Gurner joined the Australian Army Medical Corps and served in New Guinea until 1946. Following the war his association with the Army continued as a member of the Citizen Military Forces. In 1960 he returned to the Australian Army, where he rose to the positions of Director-General of Medical Services, Joint Services Medical Adviser, and Surgeon-General of the Defence Forces. From 1962 to 1979 Major-General Gurner was an Honorary Physician to Her Majesty The Queen.
Colin Gurner was a specialist in radiology and has served as President of the Royal Australian College of Radiologists.