Pilkington became a Catholic priest after his foray into politics and due to the disillusionment of the Irish War of Independence. He joined the Redemptorist Order and became known as Father William Pilkington CSsR. Pilkington served as a priest in the Diocese of Cape Town, South Africa, priest of Monmouthshire, Wales, and retired to the Redemptorist house at Bishop Eton, Liverpool, where he died in 1977.