The 42-year-old British singer threw a cup of water on Cowell and stormed off after the 57-year-old television personality made a wisecrack about her wedding night.
"I kind of imagine this would be like Mel B's wedding night," Cowell said after an escape artist had a technical malfunction during his performance. "A lot of anticipation, not much promise or delivery."
The "America's Got Talent" official Twitter account shared a gif of Brown's shocked reaction to Cowell's joke.
Brown, who filed for divorce from husband Stephen Belafonte in the spring, spoke to Entertainment Tonight after the incident.
"He should know, if you say something inappropriate he's gonna get like, stuff thrown at him," the singer explained. "In a friendly way. I made sure there was no ice in it this time... just fizzy water."
"I told him he was an [expletive] and that was it, and he goes, 'Oh, whatever,'" she added.
Mel B filed for divorce from Belafonte in March after splitting from the film producer in December after nearly 10 years of marriage.
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