Keach was born in Savannah, Georgia on June 2, 1941 to Mary Cain (née Peckham) and to Walter Stacy Keach. Keach was married four times. First to Kathryn Baker from 1964 until they divorced. Second to Marilyn Aiken from 1975 until they divorced. Thirdly to Jill Donahue from 1981 until they divorced 1986. He has been married to Malgosia Tomassi since 1986.