At the time, the former child star, now 42, was working on the movie Mermaids with Depp’s then-girlfriend Winona Ryder.
When Ricci overheard someone use the word “homophobic” on set, she asked Ryder what it meant.
Unsure what to tell the youngster, Ryder decided to phone Depp and asked him to explain it to her.
Appearing as a guest on Andy Cohen’s SiriusXM show, Ricci said that Depp is “actually the person who explained to me what homosexuality was when I was 9.”
She explained: “There was something going on on-set and someone was not being nice to someone else. And they were like, ‘oh, well he might be homophobic.’
“And then I was like, ‘well, I don’t understand what that is.’ I was in Winona’s trailer and she was like, ‘I don’t know how...’ so she put me on the phone with Johnny. And Johnny explained it to me.”
She said Depp described it in “the simplest terms” and “very matter of factly.”
“He was like, ‘it’s when a man wants to have sex with a man. And when a woman wants to have sex with a woman’ and I was like, ‘ah okay,’” she added.
Ricci has gone on to star alongside Depp in a number of films throughout her career, including 1999’s Sleepy Hollow and 1998 cult classic Fear and Loathing in Las Vegas.