Rannazzisi, born in Smithtown, New York on July 4, 1977, briefly attended the Catholic St. Anthony's High School in South Huntington, New York on Long Island, leaving after a year in what he called a mutual decision. He went on to graduate from Smithtown High School in 1996. Rannazzisi graduated from State University of New York at Oneonta, where he majored in communications. He is of Italian and Irish descent.
For 14 years, Rannazzisi said he worked in the South Tower of the World Trade Center at Merrill Lynch, on the 54th floor during the September 11 attacks, and described his experience escaping death. He said the events inspired him to move to Los Angeles and pursue stand-up comedy. In September 2015, after being contacted by a reporter from The New York Times for an article debunking his claim, Rannazzisi admitted his story was a lie.