Noel was born on 12 July 1869 in Kew, London. He was the eldest son of Roden Noel, the poet and essayist, and his wife, Alice Maria Caroline Noel (née de Broë). His father's father was Charles Noel, 1st Earl of Gainsborough.
He was educated at Winchester School and at Cheltenham College, then also an all-boys public school. He then entered Corpus Christi College, Cambridge but was rusticated (suspended) for a year and chose not to return to complete his degree.
Noel underwent training for ordination at Chichester Theological College, an Anglo-Catholic theological school. At first he was refused ordination into the Church of England because of his political beliefs: he had been offered a curacy at All Saints Church in Plymouth, but the Bishop of Exeter refused to ordain him.
Within the church at Thaxted, Noel hung the red flag and the flag of Sinn Féin alongside the flag of St George. This led to the "Battle of the Flags" with students from Cambridge leading attacks on the church to remove the flags; eventually a consistory court ruled against his displaying the flags and Noel obeyed the ruling.
He founded the Catholic Crusade to propagate his views, which had some impact in the origins of Trotskyism in Britain.
Noel also supported the British Provisional Committee for the Defence of Leon Trotsky, and signed a letter defending Trotsky's right to asylum and calling for an international inquiry into the Moscow Trials.
He was a friend of composer Gustav Holst who lived for some years in the village.
- Ought Christians to be Socialists?, 1909. Transcript of a debate with the Christadelphian Frank Jannaway.
- Oxford Dictionary of National Biography
- Conrad Noel, an Autobiography, London, J. M. Dent & Sons Ltd., 1945
- Leech, Kenneth (2004). "Noel, Conrad Le Despenser Roden (1869–1942)". Oxford Dictionary of National Biography. Oxford University Press. Retrieved 25 November 2014.
- "Noel, Conrad (Christian Socialist)". Archives and Special Collections. University of Hull. Retrieved 25 November 2014.
- Robert Jackson Alexander, International Trotskyism, 1929-1985: A Documented Analysis of the Movement. Duke University Press, 1991 ISBN 082231066X (p. 451)