Michael Sayers was born in Dublin in December 1911, the son of Philip Sayers, a Jewish-Lithuanian immigrant and businessman with Irish Republican sympathies. He was educated at Cheltenham College, and briefly studied law in London, before attending Trinity College Dublin, where he studied French under Samuel Beckett.

After graduating he returned to London. He sent some examples of his poetry to T.S. Eliot, who was impressed with his work and commissioned him to write drama criticism for Criterion. While living in London, Sayers shared flat with Rayner Heppenstall and George Orwell.

Sayers had ambitions of writing for theatre, and left London in 1936 for New York, where he worked for theatre designer Norman Bel Geddes. In 1938 he married Mentana Galleani, daughter of Italian anarchist Luigi Galleani, with whom he had two sons, Sean and Peter.

Sayers went on to take up journalism for left-wing magazines Friday and PM and for the newsletter The Hour. Through the latter he met Albert E. Kahn, with whom he collaborated in writing Sabotage, The Plot Against Peace, Great Conspiracy.

After the Second World War, Sayers had some success in writing for television, including for NBC dramas, and his play Kathleen had a short run on Broadway 1948. However, his Communist sympathies and wartime writing brought him to the attention of the House Un-American Activities Committee and he was blacklisted. He left America for a period, first for London, and then for France.

In 1955 he divorced from Mentana. While in Paris he met American painter Sylvia Thumin, and they married in 1957.

While blacklisted Sayers wrote TV scripts for Sapphire Films as Michael Connor, including for The Adventures of Robin Hood, and wrote TV dramas under his own name for British and German TV, including The Walking Stick. Sayers returned to America in 1967, when he was invited to work on screenplay for Casino Royale.

Sayers died in New York in May 2010.