Fitzgerald was born into a Roman Catholic family of Irish descent in Brooklyn. His father (also named Patrick Fitzgerald) worked as a doorman in Manhattan and a security guard at the 1964 New York World's Fair in Flushing, Queens. Fitzgerald attended Our Lady Help of Christians grammar school, before going on to Regis High School. He received degrees in economics and mathematics from Amherst College, Phi Beta Kappa, before receiving his JD from Harvard Law School in 1985. He played rugby at Amherst and at Harvard he was a member of the Harvard Business School Rugby Club.