The win for outstanding performance by a cast in a motion picture potentially sets up the movie for a major role at next month's Academy Awards.
The two leading Oscar nominees - Roma and The Favourite - were bypassed by the actors guild for a best ensemble field that also included BlacKkKlansman, Crazy Rich Asians, Bohemian Rhapsody and A Star Is Born. Although Black Panther wasn't nominated for any individual SAG Awards, it took home the final award at the Shrine Auditorium in Los Angeles.
Before a stage full of actors, actor Chadwick Boseman tried to put into context the moment for the trailblazing film, which also won for its stunt performer ensemble. "To be young, gifted and black," he said, quoting the Nina Simone song.
"We know what it's like to be told there isn't a screen for you to be featured on, a stage for you to be featured on. ... We know what's like to be beneath and not above. And that is what we went to work with every day," said Boseman. "We knew that we could create a world that exemplified a world we wanted to see. We knew that we had something to give."
The win puts Black Panther squarely in contention for best picture at the Academy Awards where it's nominated for seven honours including best picture. Actors make up the largest percentage of the academy, so their preferences can have an especially large impact on the Oscar race. In the last decade the SAG ensemble winner has gone on to win best picture at the Academy Awards half of the time.
The best picture winner at the Academy Awards has always first been nominated for best ensemble by the SAG Awards except in 1996, when Braveheart won best picture, and last year, when Guillermo del Toro's The Shape of Water overcame the SAG omission to win best picture. The actors guild instead awarded Three Billboards Outside Ebbing, Missouri its top prize.
In the lead acting categories, Glenn Close and Rami Malek solidified themselves as front-runners with wins that followed their triumphs at the Golden Globes. The 71-year-old Close, a seven-time nominee but never an Oscar winner, won best actress for her performance in The Wife. In her speech, she spoke about the power of film in a multiscreen world.
"One of the most powerful things we have as human beings are two eyes looking into two eyes," said Close. "Film is the only art form that allows us the close-up."
Malek who won the top male actor award for his performance in Bohemian Rhapsody dedicated it to Freddie Mercury, as he did at the Golden Globes.
"I get some power from him that's about stepping up and living your best life, being exactly who you want to be and accomplishing everything you so desire," said Malek.
Emily Blunt's win as best supporting actress was a shock, particularly for the actress, herself. Blunt, also nominated by the guild for her lead performance in Mary Poppins Returns, was visibly surprised. She wasn't among last week's Oscars nominees for either film.
"Guys. That truly has blown my slicked hair back," said Blunt, who praised her husband and A Quiet Place director John Krasinski as a "stunning filmmaker." ''Thank you for giving me the part. You would have been in major trouble if you hadn't."
Best supporting actor in a film went more as expected. Mahershala Ali, who won two years ago for Moonlight, won for his performance in Peter Farrelly's interracial road trip Green Book. Ali thanked his co-star, Viggo Mortensen, and Farrelly.
The Amazon series The Marvelous Mrs. Maisel won the first three awards handed out today. It won best ensemble in a comedy series, as well as individual honours for Rachel Brosnahan and Tony Shalhoub, whose win was a surprise in a category that included Bill Hader (Barry) and Michael Douglas (The Kominsky Method).
"We cannot thank you enough," said Shalhoub, speaking for the cast. "Stay with us."
Tom Hanks presented the lifetime achievement award to Alan Alda, who in July revealed that he had been living with Parkinson's disease for more than three years. The 83-year-old actor took the stage to a standing ovation while the theme to M.A.S.H. played. He said the award came at a reflective moment for him.
"And I see more than ever now how proud I am to be a part of our brotherhood and sisterhood of actors," said Alda. "It may never have been more urgent to see the world through another person's eyes. When a culture is divided so sharply, actors can help - a least a little - just by doing what we do. And the nice part is it's fun to do it. So my wish for all of us is: Let's stay playful."
For the second time, the cast of This Is Us won best ensemble in a drama series. Other TV winners included Sandra Oh (Killing Eve), Darren Criss for Assassination of Gianni Versace, Jason Bateman (Ozark) and Patricia Arquette (Escape at Dannemora).
Arquette thanked special counsel investigator Robert Mueller "and everyone working to make sure we have sovereignty for the United States of America".
Ahead of this year's show, the Screen Actors Guild also took the unusual step of publicly criticising the Academy of Motion Picture Arts and Sciences for pressuring stars to appear only on the Oscars. The film academy has declined to comment.