Christopher Nolan's historical epic takes top honor for outstanding casting ahead of next month's Oscars.
Oppenheimer has won three awards, including the top honor, at the Screen Actors Guild Awards, boosting the historical epic's chances of taking the best picture Oscar next month.
Christopher Nolan's portrayal of Robert Oppenheimer, the father of the atomic bomb, won the award for best motion picture ensemble, historically a strong Oscar predictor, at the star-studded ceremony in Los Angeles on Saturday.
Cillian Murphy, who plays the title character, won best movie actor, while his co-star Robert Downey Jr took home the best supporting actor trophy for playing his bitter rival.
“This is extremely special to me because it comes from you,” Murphy said while accepting his award.
The ceremony was the first gala hosted by SAG-AFTRA, which represents about 160,000 entertainment industry professionals, since the union held its longest strike last year.
The show also streamed live on Netflix, a first for a Tinseltown ceremony.
Kenneth Branagh, who plays Danish physicist Niels Bohr in Oppenheimer, recalled how the film's cast organized a strike since the London premiere last July when the strike was about to begin.
“We happily went in the direction of solidarity with yourselves,” Branagh said. “So this is a coming full circle moment for us,” he said to loud applause.
Oppenheimer, who has already won awards at the Golden Globes and the British Academy Film Awards, is the heavy favorite for best picture ahead of the Oscars on March 11.
The film has been nominated for 13 Oscars in total, including best director, best actor and best supporting actor, ahead of Yorgos Lanthimos' steampunk fantasy Poor Things with 11 nominations.
At the last two SAG Awards, the top five awards predicted who the eventual Oscar winners would be.
Other winners on Saturday included Martin Scorsese's Killers of the Flower Moon, for which Lily Gladstone won best actress, and The Holdovers, which earned Da'Vine Joy Randolph best supporting actress.
Barbra Streisand, winner of two Oscars and 10 Grammy Awards, received a lifetime achievement award in recognition of her six-decade career in entertainment.
