The Keeping Up with the Kardashians star went bra-less under her sheer blouse as she made her first appearance as co-host of the U.S. TV talent show, alongside fellow presenter Mario Lopez.
Kardashian seemed unaware of the nipple slip until judge Simon Cowell told her, "May I say, Khloe, you're looking very sexy tonight. I think the air conditioning's on high tonight. It's very distracting."
The brunette beauty later took to Twitter.com and tried to brush off her fashion faux pas, writing, "I think I had a little nip action earlier LOL (laugh out loud)."
It's not the first time Kardashian has been exposed on TV - her breast was clearly visible through her shirt during a morning talk show interview with her sister Kourtney last summer (11).