Fast was born in New York City. His mother, Ida (née Miller), was a British Jewish immigrant, and his father, Barney Fast, was a Ukrainian Jewish immigrant who shortened his name from Fastovsky upon arrival in America. When his mother died in 1923 and his father became unemployed, Howard's youngest brother, Julius, went to live with relatives, while he and his older brother, Jerome, sold newspapers. Howard credited his early voracious reading to a part-time job in the New York Public Library.