Mo O'Hara grew up in Pennsylvania. She moved to London because she wanted to live abroad but spoke no foreign languages. She found work as an actress and comedy performer and has performed regularly at Edinburgh and London comedy festivals. Because of her job touring around the UK as a storyteller, she decided to try writing a children's book. Her first book, My Big Fat Zombie Goldfish, was published in 2013. The series of books, by the same name, went on to become bestsellers and to be translated into several foreign languages.