The music mogul, who acted as a judge on the show from 2004 to 2010, will be seen giving Gary Barlow, Tulisa Contostavlos, Nicole Scherzinger and Louis Walsh the category that they will be mentoring for the rest of the competition, after the contestants are narrowed down to the final 24 hopefuls for the Judges' Houses stage.
However, Cowell will only be seen delivering the news to each of the four judges by phone, as he was in Miami filming The X Factor USA at the time.
It will be the first time that the 52-year-old will have appeared on The X Factor since his departure from the talent contest at the end of series seven.
Last night's Boot Camp episode controversially saw over 70 acts culled before having a chance to sing, and one singer admitting to drinking during rehearsals.
The X Factor continues tonight at 7.30pm on ITV1.
Photo Gallery - X Factor Boot Camp day two