McGowan, the second-eldest of six children (plus two half-siblings), was born in Florence, Italy, the daughter of Terri, an American writer of French descent, and Daniel McGowan, an artist of Irish descent. Daniel McGowan ran an Italian chapter of the Children of God to which both he and his wife held membership until 1978. McGowan spent her early childhood amid the group's communes, often traveling Europe with her parents. Through her father's art contacts in Italy, McGowan became a child model and appeared in Vogue Bambini and various other Italian magazines. Her parents returned to the United States when she was 10, when they divorced. She subsequently relocated to Oregon and then to Gig Harbor, Washington, where she also met childhood friend Rey-Phillip Santos. McGowan did not speak English until she moved to the U.S.
McGowan's formative years were spent with her father in Seattle, Washington, attending Roosevelt High School and Nova Alternative High School. At the age of 15, she officially emancipated herself from her parents. McGowan pursued a possible career in the film industry during her late teens, and also enrolled in a beauty school as a back-up.
