The blonde beauty learned of the honour on Wednesday, December 11, when the shortlist of hopefuls was announced and in a video shared to her Twitter account, she jumped up and down on her bed in excitement.
She got so carried away she failed to notice her robe had slipped open in front of the group of friends with whom she was celebrating.
"Whoops. Got a bit too excited about the #SAGAwards nomination for our #BombshellMovie cast... CONGRATS ALL YOU BEAUTIFUL HUMANS!!! So grateful to have gone on this journey with you all," she captioned the video. "I'm not wearing any underwear!" the Oscar winner can be heard saying in the footage.
In the movie, Theron plays Fox News journalist Megyn Kelly, who joined her female colleagues in a sexual harassment battle against late network boss Roger Ailes.
The Screen Actors Guild Awards will be held in Los Angeles on January 19, 2020.