Riegert was born in The Bronx, the son of Lucille, a piano Teacher, and Milton Riegert, a food wholesaler. Riegert grew up in Hartsdale, New York, and was raised in a nonobservant Jewish household. He graduated from Ardsley High School in 1964 and later from the University at Buffalo. He worked at a number of jobs, including teaching, waiting tables, and social worker before settling on acting as a career.