The star attended the Gay & Lesbian Alliance Against Defamation (GLAAD) 25th anniversary event on Saturday night with her girlfriend Tasya van Ree.
The couple have been together since 2008 and Heard said that she did not want to be “part of the problem” by staying in the closet.
She told AfterEllen.com: “I think GLAAD is one of the many reasons that I, as a 24 year old, can come out. I think that organisations like GLAAD make that possible because if it weren’t for opinions being changed, people being influenced, people being engaged to do the right thing, then there would be no prerogative for anyone to come out.
She added: “Like I said, I can’t be a part of the problem. I hate the idea of a label just as much as anyone else but I’m with who I’m with, I love who I love and I’m if not a better actress than I was yesterday and my personal life should have no effect on that.
“I personally think that if you deny something or if you hide something you’re inadvertently admitting it’s wrong. I don’t feel like I’m wrong. I don’t feel like millions of people are wrong because they love who they love or they were born how they were born.”
Speaking about her girlfriend, Heard, who starred in Pineapple Express, added: “She’s so beautiful. I mean, you’d have to be crazy not to want to go out with her!”