Christopher Nolan's mind-bending science fiction thriller took home the 'Original Screenplay' award ahead of Black Swan, The Fighter, The Kids Are All Right and Please Give.
Aaron Sorkin was awarded the 'Adapted Screenplay' prize for his Facebook drama The Social Network. Sorkin's script - inspired by Ben Mezrich's book The Accidental Billionaires - beat out 127 Hours, I Love You Phillip Morris, The Town and True Grit for the gong.
Sorkin's WGA victory follows his win at the Golden Globes last month.
Elsewhere, Charles Ferguson, Chad Beck, and Adam Bolt's financial meltdown movie Inside Job was awarded the 'Documentary Screenplay' prize.