He has two children, Nicholas Drew Holahan and Belle Holahan Casares, from his first marriage to Wylie O'Hara (1966–1972), and seven grandchildren. Holahan was married to Actress Loretta Swit from 1983 to 1995. Holahan is active in the area of drug and alcohol recovery and serves on the board of McIntyre House, a non-profit recovery house for men recovering from alcoholism and drug addiction located in Los Angeles. Holahan also serves on the board of Worth Our Weight, a non-profit organization in Santa Rosa, California which trains and educates teenagers and young adults who have survived foster care programs and teaches them how to work in the fine dining industry.