The pair will be joined by Ed Sheeran and Dappy at the Channel 4-hosted event, which will take place at London's Earls Court on December 11.
The cast of The Only Way Is Essex will also attend the show, which will be hosted by T4's Jameela Jamil, Nick Grimshaw, Georgie Okell, Matt Edmondson and Will Best.
The acts join a lineup already consisting of Jessie J, The Wanted, Wretch 32 and Professor Green.
Excited for the end of year party, T4 presenter Okell explained: "We called it T4 Stars for a reason and we've got them coming out of our ears!
"What better way to get ready for Christmas than to come and party with us? If you're loving the lineup, get yourself a ticket and come on down."
Tickets for the concert are on sale now. The event will be broadcast on Channel 4 and 4Music over the festive period.
> Pixie Lott names new album Young Foolish Happy
Watch the music video for Pixie Lott's new single 'What Do You Take Me For?' below: