The band will perform at London's Roundhouse on September 24, the same day their second studio album is released.
Babel is the long-awaited follow-up to 2009's Sigh No More, which reached number two on both the UK and US album charts.
"We are more than excited to release Babel into the world. We had started writing new songs well before we got into the studio to record," they said of the new record.
"At first, we peeled ourselves off the road quite reluctantly. We love playing live, obviously, but it had also become an important part of our creative process, we had been writing and rehearsing in soundchecks, and sort of 'road-testing' new songs on our very gracious audiences."
Mumford & Sons join previously announced acts such as Usher, Pink and One Direction at the free festival.
Emeli Sandé, Plan B, JLS and Jessie J are also scheduled to perform.
Fans can apply for tickets for any of the shows over on the iTunes Festival website.
Watch the teaser trailer for Babel below: