A breathless Mark Ruffalo thanked the creative team, particularly writer-director Tom McCarthy and writer Josh Singer for not taking shortcuts and honoring the survivors of the Catholic church sexual abuse scandal. The film concerned the Boston Globe reporters who investigated sexual abuse in the church.
Added co-star Michael Keaton, "This is for every Flint, Michigan, in the world. This is for the powerless. It comes down to two things. There's fair and unfair. And I'm always going to vote for fair. I'm always going to vote for the good guys."
The victory cements "Spotlight's" status as the front-runner for the best picture Academy Award.
Leonardo DiCaprio won best actor for his performance in "The Revenant." He received a standing ovation as he accepted his award.
"I'm truly humbled by this because it comes from all of you, my fellow actors," he said. He noted that he spent his teen years watching films to soak up the history of movies.
"For any young actors out there, I encourage you to watch the history of cinema," he said. "You realize we all stand on the shoulders of giants."
Brie Larson won best actress for her performance in "Room."
Alicia Vikander won the best supporting actress trophy for her performance in "The Danish Girl."
The Swedish actress, visibly overwhelmed by the honor, thanked her fellow actors.
"This is the highest honor to be allowed to join this stage," she said.
Idris Elba followed with a supporting actor win for "Beasts of No Nation" and for his performance in the TV series "Luther."
He also got off the line of the night: "Welcome to diverse TV," a tweak at the Oscars, which nominated a slate of all-white acting nominees and has gotten a great deal of backlash.
Charlotte Rampling: Welcome to Hollywood hypocrisy
All hail Burnett
Legendary comedian Carol Burnett won the Screen Actors Guild Life Achievement honor.
Burnett was greeted by a standing ovation -- and sent off to one as well.
In between, she told the story of how "The Carol Burnett Show" almost didn't happen. The network wanted a half-hour sitcom called "Here's Agnes," but Burnett had a contract that allowed her to "push the button" for a variety show.
"All the comedy-variety shows are hosted by men," the network told her. "It's really not for a gal. Comedy-variety is a man's game."
Burnett proved them wrong with an 11-year run with the top variety show on TV.
"I'm so happy I pushed that button," Burnett said before concluding with her usual signoff: "I'm so glad we had this time together."
Burnett was earning chuckles on the red carpet simply through her footwear -- what appeared to be slippers.
On TV
"Orange Is the New Black" won for comedy ensemble.
"Orange's" Uzo Aduba won the first award of the evening, for actress in a comedy series. Jeffrey Tambor won actor in a comedy series for "Transparent."
"Get up here, Dad," said presenter Jason Bateman, who played Tambor's son in "Arrested Development."
"Downton Abbey" won for drama ensemble -- a surprise, given a nomination for the final season of "Mad Men."
The SAG Awards are often punctuated by tributes to the acting profession. Given the challenge of getting roles, performers like Ty Burrell -- who was up for an acting award for his performance in "Modern Family" -- can appreciate that.
"To me, (the nomination) is just proof I'm still employed," he said to E! on the red carpet.
The 22nd annual SAG Awards ceremony aired from Los Angeles' Shrine Auditorium.
