The two US popstars will perform their respective new singles 'Boomerang' and 'All Around the World' on the March 2 show.
The lineup of celebrities taking part in the Comic Relief fundraiser for the second and third heats has also been confirmed.
This weekend's show (February 23), will feature Jon Culshaw dancing to Fatboy Slim's 'Praise You', Kim Woodburn and Rosemary Shrager dancing to 'Diamonds Are a Girl's Best Friend', and the cast of Waterloo Road mimicking the Spice Girls. This Saturday's judges include Jason Manford and Strictly star Lisa Riley.
In the final heat (March 2), Lee Nelson will be dancing to Swan Lake, Ore Oduba and Sonali Shah will perform to Outkast, while Vanessa Feltz, Lee Nelson and Keith Duffy will also be taking to the stage.
Arlene Phillips, Keith Lemon and Lee Mack will judge the final heat.
The second heat will feature a video from One Direction about their visit to Comic Relief-funded projects in Africa.
Let's Dance for Comic Relief airs on Saturday nights on BBC One.
Let's Dance for Comic Relief 2013 - show 1 pictures: