The DGA's Award for Outstanding Directorial Achievement in Feature Film is seen as a barometer for the Academy Award for Best Director.
The movie, a rags-to-riches tale about a Mumbai slum-dweller, has now won four major awards.
Boyle said at a ceremony, "I should start by curiously thanking Warner Bros. for actually having the grace to do the right thing, when I think it would have been a lot easier to do the wrong thing, and pass the film on to Fox Searchlight, who are an extraordinary bunch of people. "