In an interview on the Australian talk show "Interview", Pearce described his former co-star as "handsy".
When he was asked about what it was like working with Spacey, the actor replied: ""Yeah ... yeah. Tough one to talk about at the moment. Amazing actor; incredible actor. Mmm. Slightly difficult time with Kevin, yeah. He's a handsy guy."
He then added: "Thankfully, I was 29 and not 14."
More than 30 men have come forward with allegations of sexual misconduct against Spacey in recent months.
The allegations came to light when actor Anthony Rapp claimed Spacey assaulted him at a party in 1986, when Rapp was just 14.
Spacey subsequently took to Twitter to apologise but claimed to have no memory of the events. He has since issued an "absolute" denial of the other allegations.
Twenty allegations of inappropriate behaviour were also made against Spacey while he was artistic director of the Old Vic Theatre in London between 2004 and 2015.
In November, bosses at the theatre apologised, claiming that a "cult of personality" had contributed to the organisation's failings.
After the allegations came to light, Spacey was dropped from his lead role in the Netflix series "House Of Cards" and was replaced in the Ridley Scott film "All The Money In The World", by Christopher Plummer.
Guy Pearce isn't the first to speak about Spacey. Last week, Benicio del Toro, who appeared alongside him in the 1995 film "The Usual Suspects" said: "It's sad about the victims, number one, and sad about [him]. But the victims come first. I don't care how talented you are. I'm sorry."