Naomi Royde-Smith was born Naomi Gwladys Royde-Smith on 30 April 1875 at Craven Edge in Halifax, England. Her parents, Michael Holroyd Smith (1847-1932) and Anne (Williams) Smith (1848-1934), had 8 children - two boys and six girls - of which Naomi was the eldest. Her father was an electrical engineer working for the South London Railway. Royde-Smith attended Clapham High School in London and finishing school in Geneva, Switzerland.

Royde-Smith began her career as a literary reviewer at the Saturday Westminster Gazette. By 1912, she was the Gazette's literary editor, the first woman to hold this position. Her social circle at this time included elite literati and intellectuals, including Aldous Huxley, W.B. Yeats, and Edith Sitwell, among others.

In 1922, after Royde-Smith quit her position at the Gazette, she made her first foray into writing. Her earliest publication, The Tortoiseshell Cat (1925), is considered to be one of her best novels. Over her nearly 40-year writing career, she would produce 40 more novels and four plays. In 1926, she married the American actor Ernest Gianello Milton (1890–1974). They lived throughout England until Royde-Smith's death by renal failure at a London hospital on 28 July 1964.

By all accounts, Royde-Smith was known for her wit, vivaciousness, and commanding presence. Perhaps due in part to her own successes, she also championed previously unknown writers, publishing the early works of Rupert Brooke and D.H. Lawrence, among others.