The chef will guide viewers and his celebrity guests through cooking a Christmas dinner.
Clark wrote on his Twitter page: "FINALLY I can say ... Catch me tomorrow from 10am - 2pm live on channel 4 for Gordon Ramsay cook along live!!! Merry Christmas !!! #turkey"
Former X Factor contestant Clark was first rumoured to be appearing on the Channel 4 show earlier this month.
Stars also set to join Ramsay include Olympic boxer Anthony Joshua and I'm A Celebrity's Rosemary Shrager, as well as soap actresses Jennifer Metcalfe and Nina Wadia.
David Hasselhoff is also tipped to appear on the programme as a roving chef going out and about.
Gordon Ramsay's Cookalong Live airs tomorrow (December 25), at 10am on Channel 4.
Watch a Digital Spy video interview with Rylan Clark below: