Larsen's most notable accomplishment was pitching the only perfect game in World Series history; it is one of only 23 perfect games in MLB history. He was pitching for the New York Yankees in Game 5 of the 1956 World Series against the Brooklyn Dodgers on October 8, 1956. His perfect game remained the only no-hitter of any type pitched in postseason play until Philadelphia Phillies pitcher Roy Halladay threw a no-hitter against the Cincinnati Reds on October 6, 2010, in Game 1 of the National League Division Series.