A spokesman for the show said Tuesday that the country singer will take part in the Chicago auditions set for the end of August.
Kelly Clarkson, the original "American Idol," and one of the Jonas Brothers also may end up as guest judges. But they had yet to be confirmed Tuesday.
"American Idol" began enlisting visiting celebrities after a contract dispute led Paula Abdul to announce she was quitting the show.
There's been speculation that Abdul still could reach a deal and return for the ninth season, starting in January.