In 1939, he was selected Rhodes Scholar for Newfoundland, but delayed going to Oxford in order to join the Royal Canadian Naval Volunteer Reserve, where he served as torpedo officer.

In 1945, when he retired from the reserve he attended Oxford for a BCL degree and was admitted to the English Bar at the Inner Temple in 1948.

In 1949, O'Dea was made honorary aide-de-camp to the Governor General of Canada.

O'Dea was a member of the Board of Regents for MUN, Vice-President for Newfoundland at the Canadian Bar Association and a member of the Canadian Rhodes Scholarship selection committee.

Fabian O'Dea was also a collector of sixteenth to eighteenth century maps of Newfoundland and Labrador.