McCann made his MLB debut with the Braves on June 10, 2005 after playing in the minor leagues for the Rome Braves. A personal catcher for John Smoltz for most of the 2005 season, McCann hit his first home run in just his second regular-season game and became the first Braves player in franchise history to hit a home run in his first playoff at-bat on October 6, 2005. He accomplished the feat in the second inning of a 7–1 victory over Roger Clemens and the Houston Astros in Game 2 of the 2005 National League Division Series. McCann was named the everyday starter when the Braves traded Johnny Estrada to the Diamondbacks.