Stapledon was awarded a PhD degree in philosophy from the University of Liverpool in 1925 and used his doctoral thesis as the basis for his first published prose book, A Modern Theory of Ethics (1929).

During the war Stapledon became a public advocate of J.B. Priestley and Richard Acland's left-wing Common Wealth Party,[5] as well as the British internationalist group Federal Union.

[11] He supported implementing the recommendations of the Beveridge Report[12] and spoke at the first public meeting of the Left Book Club's "Readers' and Writers' Group".

Arthur C. Clarke, as Chairman of the British Interplanetary Society, invited him to give a talk on the social and biological aspects of space exploration.

[19] He also travelled internationally, visiting the Netherlands, Sweden and France, and in 1948 he spoke at the World Congress of Intellectuals for Peace in Wrocław, Poland.

After a week of lectures in Paris, he cancelled a projected trip to Yugoslavia and returned to his home in Caldy, where he died very suddenly of a heart attack.

His widow and their children scattered his ashes on the sandy cliffs overlooking the Dee Estuary, a favourite spot of his that features in more than one of his books.

[20] Stapledon's fiction often presents the strivings of some intelligence that is beaten down by an indifferent universe and its inhabitants who, through no fault of their own, fail to comprehend its lofty yearnings.

Clarke wrote:[19] In 1930 I came under the spell of a considerably more literate influence, when I discovered W. Olaf Stapledon's just-published Last and First Men in the Minehead Public Library.

[38] Film producer and director George Pal bought the rights to Odd John and in 1966 Castle of Frankenstein magazine reported that David McCallum would play the title role.

[39] In 2017 a multimedia adaptation of Last and First Men by Oscar-nominated Icelandic composer Jóhann Jóhannsson was released, featuring narration by Tilda Swinton and a live score performed by the BBC Philharmonic.

[40] In 2019, Justin McDonald and Kate Hodgson wrote, produced, and starred in a short film adaptation of Stapledon's "A Modern Magician."