Spacey, who was also celebrating his 64th birthday on Wednesday, began to cry and mouthed "thank you" to the nine men and three women jurors, before wiping away tears with a tissue.
The Hollywood star spoke with five of the jurors in the lobby of Southwark Crown Court, before emerging from the building to address a phalanx of journalists and photographers.
"I imagine that many of you can understand that there's a lot for me to process after what has just happened today," he said. "I am humbled by the outcome today."
He also said he was "enormously grateful to the jury for having taken the time to examine all of the evidence and all of the facts carefully before they reached their decision".
Spacey was swarmed by cameras as he then walked to a waiting taxi, as some members of the public clapped and wished him happy birthday and one woman shouted: "We love you, Kevin."
During the four-week trial, prosecutors described the actor as a "sexual bully" who had aggressively groped three of the men and performed oral sex on the fourth while he had passed out in Spacey's London apartment.
Spacey, tried under his full name Kevin Spacey Fowler, said in evidence that the case against him was weak, and that the incidents, if they had occurred at all, were consensual. He said he was promiscuous, a "big flirt" who had "casual, indiscriminate sexual encounters".
One of complainants alleged Spacey painfully grabbed his crotch like "a cobra" in the mid-2000s, an allegation Spacey described as "absolute bollocks", using a British slang term for testicles and for something which is nonsense.
While he said he might have made a clumsy pass at one of the men, he said he had never assaulted anyone and suggested that the accusers had come forward to make money.
That’s because anyone with a rational mind won’t be satisfied with the result of our judicial system. It’s a massive joke that benefits those with money.
When you live in a world that is rampant with fraud and corruption, and a world filled with judges and lawyers who are happy to accept a bribe for dishonesty, it’s really really hard to walk away from a court case with a feeling of fairness and honesty.
The court findings here aren’t enough to sway me when I see the level of bullshit that celebrities get away with.
We have too many blind idiots in the world who take things at face value. Don’t be one of those people.
Plus we're talking about things which are by their nature very difficult to prove. It's literally one person's word against another. Or in this case, nine people's word against one. All that this ruling tells us is that there was insufficient evidence to convict him beyond a reasonable doubt.
Do you think justice systems should adopt a less stringent standard for criminal convictions, like a preponderance of evidence?
No, but that also doesn't mean he's protected from the court of public opinion. Just because a court declares someone is innocent or guilty does not mean that I have to personally accept the court's decision, particularly given how often verdicts can end up being wrong.
Even if Spacey is not proven to be a rapist beyond all reasonable doubt, he is still probably a rapist based on the volume of testimony against him, and that's enough for me to distrust someone.
You say that like the opposing view isn't also the same thing, taking something (in this case, the word of the accusers) at face value.
I don't know Spacey, I have no illusions that I have zero understanding of who he is, but there's no evidence here. People shouldn't be punished for having accusations thrown at them, that's not something they control.
Sure, he could still be a terrible stain on this Earth. So could anyone.
I don't know why people have such a hard time understanding this.
You don't know Spacey and you don't know the accusers. Just because there are 9 of them doesn't make it rape.
I don't have any doubt that he "used" fame and the authority provided by celebrity to get people to agree to things that they may not have really wanted.
There's a chasm between being an egomaniac and being a predator.
So you believe he is guilty of sexual assault then... okay, I can agree with you there.