Upon the recommendation of Cardinals' executive Branch Rickey, Powel Crosley Jr., owner of the Cincinnati Reds, appointed Giles as his club's general manager on November 1, 1936, succeeding Larry MacPhail. While the 1937 Reds won only 56 games and slid into the basement of the National League, the edition improved by 26 games to finish in the first division, earning Giles the 1938 Major League Executive of the Year award from "The Sporting News". That season, he hired a future Hall of Fame manager, Bill McKechnie, to take charge of the Reds on the field. Then, on June 13, 1938, Giles swung one of the most successful trades in Cincinnati history, when he obtained starting pitcher Bucky Walters from the Philadelphia Phillies for catcher Spud Davis, pitcher Al Hollingsworth and cash.