Ruehl was born in Jackson Heights, Queens, New York City, the daughter of Mercedes J. Ruehl, a school Teacher, and Vincent Ruehl, an FBI agent. She was raised Catholic. Her father was of German and Irish descent and her mother was of Cuban and Irish ancestry. Ruehl attended College of New Rochelle and graduated in 1969. She is married to Painter David Geiser, with whom she adopted a son, Jake (born 1995). She had another son, Christopher, whom she placed in adoption in 1976; he later became Jake's godfather.