On Tuesday night, Munn stopped by Busy Tonight, where she revealed that after they met at a Super Bowl party, Foxx quickly became "like a big brother" to her. Following their initial meeting, Munn -- along with a guy she was dating -- and Foxx, 50, attended the same party.
"[Foxx] saw me at a party and I was dating this guy, who was an actor that was famous... He was my crush, and no one knew that we were dating, we were dating for a couple months," she told host Busy Philipps. "We were still at this place where you hadn't said that you're official. I was official, but I was waiting for him to, you know, say it, but it wasn't going to happen."
Because their relationship wasn't official yet, Munn, 38, and her famous date "were keeping it cool" at the party.
"I'm on one side of this party and he's on the other side as he's talking to different girls and stuff and I'm feeling so depressed. And then I decided to leave early," Munn recalled. "Jamie stops me and is like, 'Where are you going?'"
Following some back and forth -- and after Foxx caught her peering at her secret beau across the room -- Munn eventually told Foxx that she was dating the guy.
"'Is he the reason why you're leaving?'" Foxx asked Munn at the time. "I'm like, 'No, he didn't do anything wrong. You know, I just really want him to be my boyfriend, but I don't think that's really what he wants. I'm just going to go home.'"
Foxx agreed to let Munn leave, but warned that he was going to call her and leave a voicemail if she didn't pick up.
"The next morning, I got a call from Jamie and he left a voicemail," Munn said. "[Foxx] said... 'Did you come out here to be somebody's girlfriend? No! Did you come out here to be somebody's wife? No! Did you come out here just to date this guy? No! Did you come out here to be an actress? Yes! Don't you ever, ever let me see you cry about some guy like that ever, ever again. Don't you ever let some other guy make you feel like that ever again.'"
"He was just so earnest. He was just like, 'I never want to see you let any man make you feel that small again,'" Munn gushed of Foxx. "I've thought about that. Every now and then it would pop into my head, of course I've kind of veered off sometimes, but I will think about that and it brings me back to center."
Munn and Foxx posed together on the red carpet for the Mayweather vs. McGregor fight last year. At the time, it sparked romance rumors between the pair, but an eyewitness at the event told ET that there was "nothing to it."
ET spoke to the actress last month, where she opened up about the importance of removing toxicity from her life.
“It's a lesson I think you're always learning, but I think this year I really applied it, over the last year and a half, of just like, negative, toxic people just don't have a place in your life,” she said. “So, if you're around someone that's always making you feel bad, you know, you don't need them in your life."