Sarah Campion was born Mary Rose Coulton on 1 June 1906 in Eastbourne, East Sussex, England and brought up in the village of Shelford near Cambridge. She worked as a teacher in England, Canada, and Scotland; before traveling to Germany to teach English to German Jews. In 1937, the Nazis expelled her. She then travelled in Canada, the USA, South Africa, New Zealand and Australia, earning her living working as a cook until 1940, when she returned to live in England and worked in a variety of occupations.

In 1939, she stayed briefly on the Atherton Tablelands in northern Queensland, which inspired her six Australian novels, including Turn away no more (1940), Dr. Golightly (1947), Come again (1951); and "The Burdekin trilogy", including Bonanza (1942), Mo Burdekin (1942) and The Pommy cow (1944). She returned to England at the outbreak of war, where she worked as an editor, reviewer, broadcaster and fiction writer.

She married New Zealand writer, Antony Alpers in London in 1949, and emigrated to New Zealand with him and their son Philip in 1952. She became well known in New Zealand as a writer, commentator, radio broadcaster and political activist, and published no further fiction. She briefly revisited Australia in 1959, with her son Philip after her marriage ended.

Sarah Campion lived in Auckland, New Zealand until her death on 22 July 2002.