The Nashville band will be joining previously-announced headliners Arcade Fire, Kasabian and Alt-J in topping the bill at the event this June. Michael Kiwanuka is also confirmed to be performing at the three-day bash.
The largest open-air festival in the country, INmusic takes place at Zagreb's Lake Jarun on June 19-21.
The rest of the line-up is yet to be announced and previous years' line-ups included Florence + The Machine, Arctic Monkeys, The Black Keys, Placebo, The Prodigy, Nick Cave & The Bad Seeds, PJ Harvey, Moby and Morrissey.
Kings of Leon released their seventh studio album, ‘WALLS’, last October.