The music mogul revealed that he is delighted with the sales performance of the contestants' version of 'Wishing on a Star', which features JLS and One Direction.
The single is currently on course to claim the number one spot on Sunday night's official chart, following a performance of the track on last weekend's X Factor results show.
Cowell tweeted: "Heard earlier on today @TheXFactor UK charity single looks like it's going to be No.1. A massive thank you to everyone who supported this."
He added: "If you don't know about the charity @Tog4ShortLives it is run by amazing people. You're all very generous. @TheXFactor."
All proceeds made from the single will be donated to the children's charity Together For Short Lives.
Marcus Collins, Amelia Lily, Misha Bryan and Little Mix will each battle for a place in this year's X Factor final on Saturday, December 3 from 8pm on ITV1.
> 'X Factor' single: Behind the scenes with JLS, One Direction - video
Watch the music video for 'Wishing on a Star' below: