In 1932, Hartnett guided the Cubs' pitching staff to the lowest team earned run average in the league, as the Cubs clinched the National League pennant by 4 games over the Pittsburgh Pirates. Hartnett was the Cubs' catcher on October 1, in Game 3 of the 1932 World Series against the New York Yankees when Babe Ruth hit his debated "called shot." Although he hit for a .313 batting average with 1 home run, the Yankees won the series in a four-game sweep.