Festival organisers announced a wide-ranging variety of musical acts on Thursday (November 8) for the Austin, Texas concert series, including Ryan Hemsworth, Atlas Genius and Mac DeMarco.
Fear of Men, Swim deep, WHY?, Haim and NO CEREMONY/// are on the bill as well.
A full list of South by Southwest's first wave of performers can be viewed on the festival's website.
Alt-J will be appearing at South by Southwest off the heels of winning the prestigious Mercury Prize in early November for their album An Awesome Wave.
Musical acts can still apply to perform at South by Southwest 2013 by filling out an application on the organisation's website through to Friday (November 9).
South by Southwest 2013 is held from March 12 through March 17.
The Polyphonic Spree, James Blunt, Hanson, The Flaming Lips and Foo Fighters are among the acts who have played the festival since its inception in 1987.
Watch Alt-J's 'Breezeblocks' music video below: