Glass has four children and one granddaughter. Juliet (b. 1968) and Zachary (b. 1971) are his children from his first marriage, to theater director JoAnne Akalaitis (married 1965, divorced 1980). His second marriage was to Luba Burtyk; the two were later divorced. His third wife, the artist Candy Jernigan, died of liver cancer in 1991, aged 39. He had two sons, Cameron (b. 2002) and Marlowe (b. 2003) with his fourth wife, restaurant manager Holly Critchlow (married in 2001), whom Glass later divorced. Glass lives in New York and in Cape Breton, Nova Scotia. He was romantically involved with cellist Wendy Sutter for approximately five years. his partner was Japanese-born dancer Saori Tsukada.