Born at Caherina in Tralee, he joined his older brother Joe in 1901, both of them being apprentice jockeys at the famous Druids Lodge training establishment in Wiltshire England.

Victory on Lemberg in the 1910 Epsom Derby was his most famous achievement,[1] although he also rode winners in the 1,000 Guineas (Flair, 1906 and Electra, 1909), Lincoln (Uninsured, 1904), Cambridgeshire (Hacklers Pride, 1905), Eclipse Stakes (Lally, 1907 and dead heated on Lemberg in 1910), Coronation Cup (Pretty Polly, 1906) and the Grand Prix de Paris (Spearmint, 1906).

They met in 1910 and caused a scandal when, travelling together as "Mr. and Mrs. Dillon" in 1913, she was refused entry to the United States for "moral turpitude".

During World War I, Dillon served in the transport lines at Belton Park, Grantham, the Machine Gun Corps training depot.

He was portrayed by actor Tom Payne in the 2007 BBC drama Miss Marie Lloyd - Queen of The Music Hall.