Carr was born in Thornton in Craven, a village in the West Riding of Yorkshire, England, where his father James was a solicitor.

He remained at London Hospital as a resident medical officer until 1910, and then worked as a ship's doctor on a merchant vessel.

In 1911 the newly formed Royal Australian Navy (RAN) advertised in Britain for professional men to join the service, and Carr enlisted on 9 December.

During the First World War he saw service in New Guinea (where he was present at the German surrender of Rabaul), the Pacific, North Atlantic and West Indies.

Nevertheless, Carr was able to build up a system of naval medical training and facilities that proved to be effective when the RAN began to expand again in the late 1930s.