The 65-year-old actor took to social media to hit back at Pearce's recent claims, insisting the 57-year-old Australian star is "not a victim".
"Guy Pearce, I've now read the comments that you made about me and while I would have preferred not to have to play this out in the media, you obviously have your own reasons for wanting to do exactly that," Spacey said in a video posted to social media platform X.
"But, we worked together a long time ago, you know? If I did something then that upset you, you could've reached out to me. We could've had that conversation.
"But instead, you've decided to speak to the press, who are now coming after me because they would like to know what my response is to the things that you've said.
"You really want to know what my response is? Grow up."
Kevin - whose career previously went into freefall after he was accused of sexual misconduct by a number of men - recalled spending time with Pearce after they filmed 1997's LA Confidential together.
"Did you also, by the way, tell the press that a year after we shot LA Confidential, you flew to Georgia while I was shooting Midnight in the Garden of Good and Evil just to spend time with me?"
Spacey also questioned why his former co-star took so long to voice his concerns.
"Here you are now on a mission some 28 years later, after I've been through hell and back, to do what?" said the actor, who was acquitted by a jury of sexual assault charges in 2023.
"I've got nothing to hide. But Guy, you need to grow up. You are not a victim."
Spacey's retaliation came after Pearce told the Awards Chatter podcast he had been targeted by Spacey.
"I was sort of scared of Kevin because he's quite an aggressive man," Pearce said.
"He's extremely charming and brilliant at what he does - really impressive, etc. He holds a room remarkably. But I was young and susceptible, and he targeted me, no question."
In 2017 when actor Anthony Rapp accused Spacey of making sexual advances towards him when he was 14, Pearce "broke down and sobbed" when he realised how much he had been affected.
"I was in London working on something, and I heard (the reports) and I broke down and sobbed, and I couldn't stop," he said.
"I think it really dawned on me the impact that had occurred and how I sort of brushed it off and how I had either shelved it or blocked it out or whatever. That was a really incredible wake-up call."
The former Neighbours actor admitted he has since "had a couple of confrontations" with Spacey that "got ugly" but didn't share details.
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