The box office hit picked up best ensemble cast award in a motion picture, the SAG ceremony's closest thing to a best film prize.
Asked if Black Panther had changed the film industry, lead actor Chadwick Boseman replied: "My answer to that is... to be young, gifted and black."
The only British winner was Emily Blunt for her performance in A Quiet Place.
The actress picked up the prize for best supporting actress for the film, which was directed by and co-starred her husband John Krasinski.
She looked shocked as she accepted her award: "I am going to share this completely with my husband, John Krasinski, because the entire experience of doing this with you has completely pierced my heart directly. You are a stunning filmmaker."
2. Blunt was also nominated for her leading role in Mary Poppins but missed out to Glenn Close
The SAGs have well and truly blown the Oscars race wide open, with Black Panther now being considered as a serious contender for the best picture Oscar.
Bohemian Rhapsody picked up that prize at the Golden Globes, while Green Book won at the Producers' Guild of America Awards.
The winners in full
- Best actor - Rami Malek, Bohemian Rhapsody
- Best actress - Glenn Close, The Wife
- Best actor in a supporting role - Mahershala Ali, Green Book
- Best actress in a supporting role - Emily Blunt, A Quiet Place
- Outstanding performance by a cast in a motion picture - Black Panther
- Outstanding action performance by a stunt ensemble in a motion picture - Black Panther
- Best actor in a drama series - Jason Bateman, Ozark
- Best actress in a drama series - Sandra Oh, Killing Eve
- Best actor in a TV series or limited series - Darren Criss, The Assassination of Gianni Versace: American Crime Story
- Best actress in a TV series or limited series - Patricia Arquette, Escape at Dannemora
- Best actor in a comedy series - Tony Shalhoub, The Marvellous Mrs Maisel
- Best actress in a comedy series - Rachel Brosnahan, The Marvellous Mrs Maisel
- Outstanding performance by an ensemble in a drama series - This Is Us
- Outstanding performance by an ensemble in a comedy series - The Marvellous Mrs Maisel
- Outstanding action performance by a stunt ensemble in a comedy or drama series - Glow
- Life achievement award - Alan Alda
Despite four SAG nominations, Bradley Cooper's A Star is Born could be on the wane after failing to pick up a single prize.
Glenn Close beat The Favourite star Olivia Colman to take home the best actress prize for her role in The Wife, replicating her success at the Golden Globes.
4. Glenn Close feels the love - could she be in line for an Oscar at her seventh attempt?
Rami Malek achieved the same repeat success, picking up the best actor award for playing Freddie Mercury in Bohemian Rhapsody.
Mahershala Ali was honoured with the best supporting actor prize for his part in Green Book, beating British hopeful Richard E Grant (Can You Ever Forgive Me?)
The SAGs also honour the stars of television and it was Amazon Prime series The Marvellous Mrs Maisel which swept the comedy prizes, taking the award for best ensemble in a comedy series, as well as best actress in a comedy series for Rachel Brosnahan and best actor in a comedy series for Tony Shalhoub.
6. Lupita Nyong'o and Chadwick Bose are in celebration mode backstage
The prize for best ensemble in a TV drama went to This Is Us.
Best actor went to Jason Bateman for Ozark, with Sandra Oh honoured with best actress for Killing Eve.
Other TV winners included Patricia Arquette for Escape at Dannemora and Darren Criss for The Assassination of Gianni Versace.
Black Panther also won best action performance by a stunt ensemble.