Chadwick Boseman, who plays the title role in what was the top-grossing film in North America in 2018, explained the film's significance alongside his co-stars, almost all of them black.
"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. Has it actually changed the way this industry works and how it sees us?'"
"Black Panther" also won for best stunt ensemble.
As the Oscars wrestle with various issues, the SAG Awards seemed to sidestep all of those landmines and controversies.
The best picture victor 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 previous year, when Guillermo del Toro's The Shape of Water overcame the SAG omission to win best picture.
Despite four nominations, Oscars frontrunner A Star is Born failed to pick up an award.
One major absentee at the 25th edition of the SAG Awards was Alfonso Cuaron's "Roma" - the top Oscar nomination getter was left out of SAG contention.
Alda, an actor, director and screenwriter with a long list of credits to his name, is best remembered by television audiences as Hawkeye Pierce in the Vietnam War comedy series M*A*S*H.
The Amazon series "The Marvelous Mrs. Maisel" won the first three awards handed out Sunday at the Shrine Auditorium in Los Angeles.
The nominees include many of this year's awards season favourites, including Christian Bale for Vice, Bradley Cooper for A Star Is Born, Rami Malek for Bohemian Rhapsody, Lady Gaga for A Star Is Born, Glenn Close for The Wife and Emily Blunt for Mary Poppins Returns.
"I am just really grateful to be amongst this fraternity of people, amongst this fraternity of artists who have the good fortune of getting to deal and wrestle with the human condition and trying to do that responsibly", he said.
The only British victor was Emily Blunt for her performance in A Quiet Place. "You are a stunning filmmaker".
The prize for best ensemble in a TV drama went to This Is Us.
In the TV categories, Sandra Oh's much-lauded performance in Killing Eve netted her the award for best female actor in a drama series, while Jason Bateman received the corresponding award for a male performer for his performance in the money laundering family drama, Ozark. That we could create a world that exemplified a world we wanted to see. "Actors can help, a little, just by doing what we do".