The King's Speech won the best-actor trophy for Colin Firth and a second honour for its overall cast at the Screen Actors Guild Awards.
The two prizes capped a week-long surge of Hollywood honours for the monarchy saga, which is building momentum for the February 27 Academy Awards, where the Facebook drama The Social Network previously had looked like the favourite.
Natalie Portman earned the best-actress award at the Screen Actors ceremony for Black Swan, while The Fighter co-stars Christian Bale and Melissa Leo swept the supporting-acting honours, boosting their own prospects come Oscar night.
The King's Speech leads Oscar contenders with 12 nominations, among them best picture and actor for Firth, who has been the awards favourite virtually since the film premiered at festivals half a year ago.
"Until today, I would say probably, if ever I felt that I had a trophy which has told me that something's really happening for me, it was my SAG card," said Firth, who plays the Queen's father, George VI, as he takes the throne in the 1930s while struggling to overcome a debilitating stammer.
"Growing up in England, it's not something you expect to see in your wallet, really," Firth continued.
"And so it has this glow, and I used to flash it around, hoping it would get me female attention, entry into nightclubs and top-level government departments. It didn't."
Many winners had gushing words for the protection and fellowship their union offers.
"I've been working since I was 11 years old, and SAG has taken care of me," said Portman, who won for her role as a ballerina losing her grip on reality.
"They made sure I wasn't working too long and made sure I got an education while I was working."
Bale is a strong favourite for the supporting-actor Oscar as real-life fighter Dicky Eklund, whose career unravelled amid drugs and crime.
Eklund briefly joined Bale on stage, the actor telling him he's "a real gentleman".
"I love acting. I love what we do," Bale said. "It's so bloody silly at times, isn't it? It's like playing dress-up, and other times it is so meaningful. I just enjoy that so much - we get to walk in other people's shoes. Life without empathy is no fun at all."
Leo, who plays the domineering matriarch of Eklund and half brother Micky Ward's boxing family in The Fighter, was speechless for a long moment after taking the stage.
"I'm much better when I have my words written for me and somebody's costumes to put on," said Leo, 50, an Oscar nominee two years ago for Frozen River who had success earlier in her career on TV's Homicide: Life on the Street but has caught a second wind at an age when many actresses find roles scarce.
"This has been an extraordinary season for me."