C. Tate Regan studied zoology at Queen's College, Cambridge, graduating as Master of Arts (MA) in 1901. That same year he was appointed to the staff of the British Museum (Natural History) as assistant to the reptile and fish expert G.A. Boulenger*. In due course Regan became responsible for the museum's fish collection and in 1921 was promoted to keeper of the Department of Zoology. He became director of the museum in 1927, holding this position until his retirement in 1938.
Regan wrote well over 200 publications, most of them specialised papers on fishes, particularly their skeletal anatomy and its use to elucidate their evolution and taxonomic relationships. His comprehensive classification of fishes was accepted internationally as a basis for further taxonomic work. His major works were The freshwater fishes of the British Isles (1911), Fishes (British Museum, 1914), The fishes of the families... (with E. Trewavas, 1929, 1930, 1932), and Natural history (editor, 1936). He described the fishes collected by J. Stanley Gardiner* in the Indian Ocean (1908), as well as those collected by the British Scotia and Terra Nova Antarctic expeditions and the Danish Atlantic and Mediterranean expeditions. He was elected a Fellow of the Royal Society of London in 1917 and was awarded an honorary Doctor of Science (DSc) degree by Durham University in 1929.
Between 1906 and 1921 Regan contributed a number papers on South African marine fishes to local journals. In the first two he described new species from the coasts of KwaZulu-Natal and the Cape Colony in the Annals of the Natal Museum (1906, 1908, Vol. 1). A further five papers by him appeared in the Annals of the Durban Museum, in which he described fishes collected in Natal by Mr Romer Robinson* (1914-1917, Vol. 1), at Durban by Robinson and H.W. Bell-Marley* (1919, Vol. 2), and by Bell-Marley (1921, Vol. 3); and reviewed the flat-fishes of Natal (1920, Vol. 2).