C.S. Lewis became a Christian in 1931 after a major change in his religious beliefs.
Lewis had abandoned Christianity during his adolescence and described himself for many years as an atheist. His return was gradual rather than the result of one isolated event. Conversations with fellow writers, especially J.R.R. Tolkien and Hugo Dyson, helped him reconsider the possibility of Christianity. Lewis later referred to his conversion as taking place in 1931.
On 28 September 1931, Lewis wrote to his friend Arthur Greeves that he had passed from believing in God to believing in Christ. Tolkien and Dyson had spoken with him about myth, history, and the Christian understanding of the Gospels during a late-night conversation at Magdalen College, Oxford.
Lewis’s conversion did not immediately make him an Anglican public writer. His later apologetic books and broadcasts developed over the following decade, particularly during the Second World War.