The Harry Potter star plays beat poet Allen Ginsberg in the John Krokidas-directed movie, which has been bought by Sony Pictures Classics.
The deal - which The Hollywood Reporter believes to be in the region of $2 million (£1.26 million) - is for distribution in the US, eastern Europe, South Africa, Australia and New Zealand.
"To be considered amongst the ranks of Pedro Almodóvar and Woody Allen is beyond my wildest dreams," said Krokidas.
"Sony Pictures Classics is truly the perfect place for this film. This is a dream come true."
Kill Your Darlings premiered at Sundance last Friday (January 18), and is screening in competition at the festival.
The movie also stars Elizabeth Olsen, Michael C Hall and Chronicle's Dane DeHaan.
Boardwalk Empire's Jack Huston plays Ginsberg's contemporary Jack Kerouac, with Contraband actor Ben Foster as William S Burroughs.
Photo gallery - 'Kill Your Darlings' films in New York City: