Margulies was born in Brooklyn, New York, the son of Runya (née Zeltzer), a nurse and museum worker, and Harry David Margulies, a lawyer.[1] Margulies graduated from City College of New York. Immediately afterward, he made his stage debut in the off-Broadway play Golden 6 (1958). His first Broadway appearance was in the 1973 revival of The Iceman Cometh.