Both acts will guest on the Sunday, November 8 results show.
Lewis, the 2006 X Factor winner, will perform her new single 'Happy' ahead of the release of her second album Echo on November 16.
Black Eyed Peas will play 'Meet Me Halfway', the third single from their number one LP The E.N.D.
The X Factor continues this Saturday at 8pm on ITV1. Bon Jovi and boyband JLS will perform on Sunday's results show.