Denis Santry was born in Cork on 14 May 1879 the son of Denis Santry senior, a carpenter and joiner, and his wife Ellen. He was apprenticed as a cabinet maker, before winning an Armott Scholarship to the Cork Municipal School of Art in 1894. He attended Crawford School of Art in 1895, and in 1896 he was articled to architect James Finbarre McMullen. He won a Cork Exhibition scholarship to the Royal College of Art in South Kensington, London, in 1897-98, where he won the Queen's prize for freehand drawing. He then returned to McMullen's office, where he worked from 1899 until 1901.