The film's star, Colin Firth, continued his awards-season sweep, taking home SAG's best actor prize for his role as a stammering King George VI.
Natalie Portman was named best actress for her role as an unhinged ballerina in "Black Swan."
The supporting prizes went to Christian Bale and Melissa Leo for "The Fighter."
The SAG awards are a good indicator of Oscar success because actors in the U.S. film and TV industry make up the largest voting group among members of the Academy of Motion Picture Arts and Sciences. The Oscars will be handed out on Feb. 27.