Denis Santry was born in Cork, Ireland on 14 May 1879, the son of a carpenter and joiner, also called Danis Santry. After serving an apprenticeship as a cabinetmaker, he studied at Cork Municipal School of Art from 1894 to 1896. He also attended Crawford School of Art in Cork in 1895. In 1895 or 1896 he was articled to James Finbarre McMullen (1859-1933) in Cork. He received a national bursary enabling him to study at the Royal School of Art in Kensington, London in 1897-98, during which time he won the the Queen's prize for freehand drawing. He then returned to McMullen's office where he worked for the next two years. In 1901 he moved to South Africa, apparently for health reasons. He settled in Cape Town and over the next decade worked for various architectural firms. It is unclear if he had his own practice at this time. During this period he also worked as a painter and cartoonist. From 1903 his cartoons appeared in local newspapers and magazines including the South African Review. He usually used the pseudonym 'Adam'. Around 1910 he seems to have temporarily abandoned architecture in favour of cartooning. He also started working as an art metalworker and sculptor, and began making animated films.
In 1918 Santry joined the Singapore-based architectural firm Swan & McLaren as a partner. He remained in Singapore until 1934 when he retired to England. He returned to South Africa in 1940 and resumed his practice after the Second World War. He executed a number of private houses near Hillcrest, Natal.
Santry was admitted to the Institute of South African Architects in 1950. He was at one time President of the Institute of Architects of Malaya and involved in the formation of the Singapore Society of Architects in 1923 and the Institute of Architects of Malaya in 1930. He died in Durban, South Africa on 14 April 1960.