Hewes, whose mother was a theatrical producer, began his career as a copy boy in the theater department of The New York Times. After writing some stories for the Sunday arts pages, Hewes moved over to the weekly The Saturday Review. At first he served as a second-string critic for The Saturday Review but he eventually took over as chief critic, holding the position from 1955 to 1973. He was known for his attention to theater outside of New York. In 1974, he founded the American Theater Critics Association. He also had a hand in the establishment of the regional theater Tony Award.
Hewes is survived by his wife, three sons and six grandchildren.