Britain's Got Talent winners will take to the stage on Sunday 5 July
The dance troupe won Britain’s Got Talent last month, beating favourite Susan Boyle.
They’ll join Kanye West, Kelly Rowland, N-Dubz and Alesha Dixon at the two-day festival in London’s Hyde Park.
Other acts to perform include Basement Jaxx and Dizzee Rascal.
Diversity are also taking part in the Britain’s Got Talent live tour, which kicks off at Birmingham’s NIA on 12 June.
Wireless Festival 2009 takes place on 4-5 July.