The US hip-hop group made up of Jneiro Jarel and DOOM will play on the night of Friday, September 7 at the festival's RizLab stage.
To mark the announcement, the duo have unveiled new track 'Rhymin' Slang' from the forthcoming JJ DOOM album Key to the Kuffs.
Already announced to play at the four-day music event next month are songwriting legend Stevie Wonder, Florence + the Machine, New Order, Sigur Ros, Friendly Fires, The xx and Gary Numan.
Other additions to Bestival include Kate Nash, Stooshe, Summer Camp, The Correspondents, James McCartney and The Coronas.
Bestival takes place at Robin Hill Country Park on the Isle of Wight between September 6 and 9.
Listen to JJ DOOM track 'Rhymin' Slang' below: