She was born in Schenectady, New York, and grew up in Fitchburg, Massachusetts. Cadigan was a student at the University of Massachusetts and the University of Kansas. She studied with James Gunn at Kansas and graduated in 1975. That same year Cadigan joined the convention committee for MidAmeriCon, the 34th World Science Fiction Convention being held in Kansas City, Missouri over Labor Day weekend 1976. Her job as a committee member was to help guest of honor Robert A. Heinlein.