Career
O'Callaghan became involved in the sport of Thoroughbred horse racing as an apprentice jockey in his native Ireland. In 1982 he emigrated to the United States where he studied at Miami Dade Community College in Florida. In 1988, he went to work as an assistant to trainer Thomas J. Skiffington, Jr.
In 1990, O'Callaghan set up his own public stable, handling fifteen horses from prominent owner, Frank Stronach.
