Schwartz was born in 1927 and was raised in Brooklyn, New York. After a stint in the navy, Schwartz became interested in writing. He got his bachelors degrees from Colby College and a masters in journalism from Northwestern University. He reported for The Binghamton Press from 1951 to 1955.
He is best known for the Scary Stories to Tell in the Dark series, which featured gruesome, nightmarish illustrations by Stephen Gammell. The series was America's most frequently challenged book (or book series) for library inclusion of 1990-1999.
Some of his other books, such as When I Grew Up Long Ago, were aimed at an older audience, and presented glimpses of life in the United States during the late 18th century and the early 19th century. In his later years, Schwartz lived and wrote in Princeton, New Jersey. He died in 1992 and was survived by his wife of 37 years and their four children.