Spacey's decision to open up about his sexuality comes hours after a Buzzfeed News report was published in which actor Anthony Rapp alleged that Spacey made sexual advances on him when he was 14 years old, and Spacey was 26.
In a statement posted to Twitter on Sunday night, Spacey wrote, "I have a lot of respect and admiration for Anthony Rapp as an actor. I’m beyond horrified to hear his story."
"I honestly do not remember the encounter, it would have been over 30 years ago," he continued. "But if I did behave as he describes, I owe him the sincerest apology for what would have been deeply inappropriate drunken behavior, and I am sorry for the feelings he describes having carried with him all these years."
The House of Cards star went on to say that Rapp's story "has encouraged me to address other things about my life."
"I know that there are stories out there about me and that some have been fueled by the fact that I have been so protective of my privacy," he continued. "As those closest to me know, in my life, I have had relationships with both men and women. I have loved and had romantic relationships with men throughout my life, and I choose now to live as a gay man."
"I want to deal with this honestly and openly and that starts with examining my own behavior," Spacey concluded.
In the Buzzfeed interview, published on Sunday, Rapp alleges that he met Spacey at a post-show event when both performers were starring in separate Broadway shows.
The now-46-year-old actor claims that he went to a party a Spacey's apartment a few days later and that, as the party ended, Spacey picked him up, placed him on his bed, and climbed on top of him, making a sexual advance.
Rapp alleges that Spacey appeared to be drunk and that "he was trying to seduce me."
"I don't know if I would have used that language. But I was aware that he was trying to get with me sexually," the actor said in the interview.
Rapp said that thinking of the alleged incident is still "deeply confusing" for him.
"My stomach churns," he said. "I still to this day can't wrap my head around so many aspects of it."
Rapp additionally said that he's never publicly accused Spacey in the past, but he is coming forward now in the wake of the allegations against Hollywood producer Harvey Weinstein.
"Part of what allowed the Harvey situation to occur was that there was this witting and unwitting conspiracy of silence," he said. "The only way these things can continue is if there's no attention being paid to it, if it's getting forgotten."
Following the Buzzfeed report, Rapp told ET in a statement, "I came forward with my story, standing on the shoulders of the many courageous women and men who have been speaking out, to shine a light and hopefully make a difference, as they have done for me."