Hartnett had another impressive season in 1935 when he produced a .344 batting average, third-highest in the league and led the league's catchers in assists, double plays, and fielding percentage. He also led the Cubs pitching staff to the lowest earned run average in the league as they won the National League pennant by 4 games over the St. Louis Cardinals. For his performance, Hartnett was named the recipient of the 1935 National League Most Valuable Player Award. The Cubs lost to the Detroit Tigers led by Mickey Cochrane in the 1935 World Series.