Leto, 41, returned to acting after a six-year hiatus to play the role, and had widely been expected to win the Oscar. It was his first nomination.
“To all the dreamers out there all around the world watching this tonight, in places like the Ukraine and Venezuela, I want to say, we are here, and as you struggle to make your dreams happen, to live the impossible, we’re thinking of you tonight,” Leto said, upon accepting the award.
The other nominees Sunday were Barkhad Abdi, “Captain Phillips”; Bradley Cooper, “American Hustle”; Michael Fassbender, “12 Years a Slave”; and Jonah Hill, “The Wolf of Wall Street.”
“Dallas Buyers Club” also won the Academy Award for Make-up and Hairstyling.
The 86th Academy Awards are airing live on ABC from the Dolby Theatre in Los Angeles, hosted by Ellen DeGeneres.