He was given the prize for best leading actor in a play, for playing a young gay man living with Aids in the sprawling, seven-hour revival Angels In America.
Garfield dedicated the win to the LGBTQ community, who he said fought and died for the right to love. He said the play is a rejection of bigotry, shame and oppression.
"We are all sacred and we all belong," Garfield said.
He then referenced last week's US Supreme Court decision stating: "(Let's) just bake a cake for everyone who wants a cake to be baked."
His comments were met with a rousing applause.
Judges at the Supreme Court ruled 7 to 2 in favour of Jack Phillips last week.
They said his rights had been violated under the first amendment.
They also suggested the Colorado Civil Rights Commission, who took the case against Phillips, showed hostility to religion.
Stay up to date with the latest news stories from a Christian perspective. Sign up to our daily newsletter and receive more stories like this straight to your inbox every morning.
