Neil Simon was born on July 4, 1927, in The Bronx, New York, to Jewish parents. His father, Irving Simon, was a garment salesman, and his mother, Mamie (Levy) Simon, was mostly a homemaker. Simon had one older brother by eight years, television writer and comedy teacher Danny Simon. He grew up in Washington Heights, Manhattan during the period of the Great Depression, graduating from DeWitt Clinton High School when he was sixteen, where he was nicknamed "Doc" and described as extremely shy in the school yearbook.
Simon's childhood was difficult and mostly unhappy due to his parents' "tempestuous marriage" and financial hardship caused by the Depression. He would sometimes block out their arguments by putting a pillow over his ears at night. His father often abandoned the family for months at a time, causing them further financial and emotional hardship. As a result, Simon and his brother Danny were sometimes forced to live with different relatives, or else their parents took in boarders for some income.
To escape difficulties at home he often took refuge in movie theaters, where he especially enjoyed comedies with silent stars like Charlie Chaplin, Buster Keaton, and Laurel and Hardy. Simon recalls: "I was constantly being dragged out of movies for laughing too loud. "