Dorothy Delius Allan Black was born on 27 March 1890 in Bradford, Yorkshire, England, UK. She was the daughter of Clare Delius (1866–1954), and her husband J. W. A. Black, her parents married in 1889. She was niece of the famous composer, Frederick Delius (1862–1934). Her mother wrote her brother's biography: Frederick Delius: Memories of my Brother. She married in 1916 with Hugh MacLeish.

She started to write very young, and had published novels since 1916. She used her maiden name Dorothy Black and the male pseudonym, Peter Delius. At first, she wrote diferent tipes of books, includes poetry and children's fiction, before center in romance fiction. She travelled widely as inspiration for her books set in diferent parts of the world. In 1934 published anonymously "Letters of an Indian judge to an English gentlewoman", later reedited under her name. During the summer of 1949, she assisted the writer Marion Crawford, who was writing a series of features on life with Princess Margaret. In 1960, Dorothy wrote her auto-biography "The foot of the rainbow", center in her writing career. In total, she published over a hundred of novels and several short stories.

Dorothy became a vice-president of the Romantic Novelists' Association, along with the mediatic writer Barbara Cartland. She passed away in 1977 in Scotland, UK.