Daughter of Sir Edward and Lady Mitchell, Mary Mitchell was based in Melbourne, where Sir Edward was a barrister. She was one of four daughters.
She travelled with some regularity from 1906 onwards; after the success of A Warning to Wantons, she spent a year in London (with winter in Majorca and Spain and a period in Norway and Sweden) in the early 1930s. She was an early member (and first female president) of the Victorian branch of the PEN Club, alongside Myra Morris, M. W. (Marie) Peacock, Georgia Rivers, Dorothy Blewett, Capel Boake, Jean Campbell, Kathleen Dalziel, and Tarella Quin Daskein.
Mitchell went blind later in her career, but continued her work with the aid of touch-typing and dictaphones, writing a further eight novels after her eyesight deteriorated. In 1970, she was appointed M.B.E.
