Jo Duffy was born in New York. She attended Wellesley College.
Mary Jo Duffy is an American comic book writer and editor. She began her career working for Marvel Comics. Duffy would make her debut as a writer on DC Comics in 1987 with Batman #413. She continued writing for DC and Dark Horse comics. Her best known work in DC is writing the first 14 issues of Catwoman. She continued writing for Marvel in the early 2000's. She is currently working as a receptionist at the US Immigration Office in New York and has been largely absent from the publishing scene for more than a decade. She started her own company to self publish her works but as of 2013, the company is listed as inactive as no works were ever published.