Born in Windsor, England in 1944, Nimmo's father died when she was only five. By the time she was fourteen, she had gone to two boarding schools and had joined a theater company in England. Her unstable childhood led to a series of diverse jobs where she worked in several fields as a nanny, a photographic researcher, and a floor manager at the BBC. At the BBC she became a director of Jackanory, a children's show. After having her first child, Nimmo left the BBC and began work on her first novel, "The Bronze Trumpeteer." She is widely known for her Charlie Bone character and the Children of the Red King series. She currently resides in Wales with her husband.