Azealia Banks, Billy Bragg and St. Vincent are also due to appear at the Gothenburg event.
Way Out West 2012 will run for three days starting from August 9.
The show, which is held in a 137 hectare park, won the 'Most Innovative Festival' award at last year's MTV O Music Awards.
The 2011 lineup included Pulp, Noah and the Whale, Fleet Foxes and The Hives.
One of last year's more notable moments saw Kanye West join Prince on stage.
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Watch the Florence + The Machine 'Lover To Lover' music video below: