The drama about the founding of Facebook also won awards for director David Fincher and screenwriter Aaron Sorkin.
It beat nominees "Black Swan," "Inception," "127 Hours" and "Toy Story 3."
"Inception" was the film most honored by the group, with four awards: Best Original Screenplay (Christopher Nolan), Best Art Direction (Luke Freeborn, Brad Ricker and Dean Wolcott), Best Cinematography (Wally Pfister )and Best Score (Hans Zimmer).
Colin Firth won Best Actor for his portrayal of a stammering monarch in "The King's Speech."
Jennifer Lawrence won Best Actress for playing a young woman struggling to save her Missouri backwoods home in "Winter's Bone."
"The Fighter" rung up two winners: Best Supporting Actor Christopher Bale and Best Supporting Actress Melissa Leo.
Ben Affleck's crime thriller "The Town" won for Best Acting Ensemble.
"This was easily the most competitive ballot in the history of our association," said WAFCA president Tim Gordon. "We have never had so many tight races."
"Toy Story 3" won for Best Animated Feature.
Best Documentary was "Exit Through the Gift Shop."
"Biutiful," starring Javier Bardem, was named Best Foreign Language Film.
WAFCA, which includes 50 members from the D.C., Maryland and Virginia areas, announced its winners Monday morning.
A complete list of winners and nominees can be found on their website.