Harris was born on 28 April 1884 at Pantysgallog, Dowlais, Glamorgan in south Wales. He studied at Merthyr Tydfil County School and St David's College, Lampeter (obtaining a first-class BA degree in Welsh in 1910). He won an Meyrick scholarship to Jesus College, Oxford where he obtained a BLitt in 1913 and a BA in Theology in 1914. He was ordained deacon in 1913 and priested in 1914. After initially being curate of Ystradgynlais, he moved to Christ Church, Swansea in 1917 and then to All Saints, Oystermouth in the following year. He was appointed Lecturer (1919) and then Professor (1940) of Theology at St David's College, Lampeter, becoming Professor of Welsh in 1941. He was also Precentor of St David's Cathedral (1933), becoming canon of the cathedral in 1937 and Treasurer in 1948. He died in London on 23 January 1956.

Harris was a supporter of the catholicity of the Church in Wales, and was a founder member of the St. David's Society which was set up to promote this. He wrote on this and on other theological topics, and served on committees for the Welsh Church Hymnary (translating some of the hymns himself) and the Book of Common Prayer. He was a member of the Gorsedd of Bards, with his bardic name being "Arthan". He also translated the office of Compline into Welsh in 1941.