With Boston, Kielty saw limited action as the 4th outfielder, appearing in 20 games, hitting .231 with 1 HR and 9 RBI. He saw no action in the Red Sox playoff series against the Los Angeles Angels of Anaheim, which the Red Sox swept. In the ALCS against the Cleveland Indians, Kielty played in games 1 and 5 due to his past success against Cleveland starter CC Sabathia, hitting .400 with 2 RBI, and helping the team advance to the World Series.