The musical fundraiser will collect money for the children's charity and will feature performances from former stars of the ITV1 talent show.
"It's an honour to be able to support ChildLine at this fantastic event. I'm looking forward to seeing some familiar X Factor faces and hopefully we'll raise lots of money to help ChildLine continue its brilliant work," said Flack.
Dickson said: "Following last year's highly successful ball at The Savoy which raised an incredible sum of money for ChildLine, I am delighted and honoured to be able to help again this year and I'm looking forward to it immensely."
The ChildLine Ball takes place on October 18 at the Savoy Hotel, and will feature classic introductions for the acts from Dickson.
Last year's ball raised £640,000 for the charity.
Listen to X Factor winners Little Mix's new single 'Wings' below: