The 43-year-old father-of-three, who has lost a reported 28lbs to play AIDS victim Ron Woodroof in upcoming movie Dallas Buyers Club, looked swamped in his smart three-piece suit and overcoat as he picked up an award for best supporting actor for his comedic roles in Bernie and Magic Mike.
During his acceptance speech, the actor said: "Tonight I'm here because I did work that you liked. It feels good, I was able to humble myself to who these guys were. They're both outsiders. I had a ball diving into their obsessions."
McConaughey was joined by Jessica Chastain, Rachel Weisz, James Gandolfini and Michael Shannon at the ceremony and dinner held at the Crimson Club.
Weisz was honoured as best actress for her role in The Deep Blue Sea, Kathryn Bigelow best director, and her thriller Zero Dark Thirty movie, starring Chastain, won best movie.
Daniel Day-Lewis was awarded best actor for his role as president Abraham Lincoln in Lincoln, and his on-screen wife Sally Fields picked up best supporting actress.
McConaughey's Dallas Buyers Club co-star Jared Leto recently revealed his extreme weight loss to play HIV-positive transvestite Rayon.
See more stars and their shocking weight loss for film roles: