Anne Fremantle belonged to a prominent English family and grew up in an atmosphere of social, artistic, and political awareness. Three-Cornered Heart (1970) provides a richly detailed, affectionate account of the Victorian girlhood of Fremantle's mother and of her own Georgian childhood, with some references to her adult life.
Fremantle attended Cheltenham Ladies College, and was a scholar of Lady Margaret Hall, Oxford, where she obtained an M.A. in history. With her artist husband, Christopher Fremantle, she had three sons. Her career as a journalist began in 1931 in London, where she worked on the London Mercury and New Statesman and reviewed regularly for the Times Literary Supplement. She was defeated as a Labour Party candidate in the 1935 general election. At the beginning of World War II, Fremantle drove an ambulance for the London County Council and made broadcasts in French and German for the BBC. In 1940 she came to the U.S. and worked in the British Embassy in Washington, D.C., becoming an American citizen in 1947. Fremantle worked for 10 years at the United Nations as an editor.
Fremantle combined journalism with academic positions at Fordham University in New York (1948-61) and New York University (1971-79) and was a fellow at Wesleyan University Center for Advanced Studies in Connecticut (1966). She has been an editor for the Catholic Book Club and Commonweal, and made frequent radio and television broadcasts, for NBC's The Catholic Hour and CBS' Invitation to Learning, among others.