The 26-year-old performer won the 2006 series of The X Factor but will be making an appearance on the new American competition, which is set to start in May on the US channel Bravo.
The show sees former American Idol judge Kara DioGuardi taking a seat on the panel and guest judges will include stars such as Donna Summer, Taio Cruz and Natasha Bedingfield.
The winner will be given a record contract as well as a publishing deal.
Lewis has been spending more and more time in the US since she won The X Factor five years ago.