The boyband will take to the stage at London's Roundhouse on September 6 for a free-ticketed gig.
Fans can apply for tickets now through the official iTunes Festival website or the dedicated app.
Olly Murs, One Direction and Rebecca Ferguson are among the other X Factor alumni to perform headline shows at the month-long series of events.
Noel Gallagher, Norah Jones, Usher, Emeli Sandé and Jack White have also been confirmed for intimate sets at the London venue.
JLS are currently working on their fourth studio album, which is expected to be released later this year.
Watch the music video for JLS's 'She Makes Me Wanna' below: