The actor was asked about his experience working alongside Spacey during an interview with the "Jim and Sam Show," where they also spoke about the numerous sexual misconduct allegations levied against him in recent days.
Though the "Walking Dead" alum called watching Spacey in "The Iceman Cometh" a few years back a "unbelievably transformative experience," his opinion of him changed after they got to work on Edgar Wright's movie.
"When I was there, he really rubbed me the wrong way. I thought he was a bit of a bully," Bernthal explained. "I didn't really care for the way he was behaving toward some of the other people on set."
When asked if he meant "sexually or aggressive," Bernthal said it was a "combination" of both. "I think he was acting towards people in a way that I remember at the time thinking, man if that was a woman he was talking to, I would have done something and I would have said something," he continued. "I was really happy to get out of there."
"I just remember losing a ton of respect for him. Nowhere did I see anything like some of the allegations that have come up against him and it would be weak of me to pile on about some shit that I don't know about, but the kind of man he was when I saw him, working with him, made me lose all respect for him and I was enormously disappointed," he added.
Bernthal said he had heard "stories" about Spacey before taking the gig, but walked onto set with "immense respect for the guy."
"That's what I walked in with and it didn't take a long time for me to change my mind," he said.