The "Piece of Me" singer was performing at The Theater inside MGM National Harbor in Maryland.
She was seen adjusting her sparkly black bra during a set change halfway through her 2005 hit "Do Somethin'.
The adjustment she made didn't exactly work, as she continued performing with her nipple hanging out for several minutes!
To make matters worse, none of her dancers noticed or told her.
This isn't the first time she's experienced some sort of wardrobe malfunction. One of her breasts popped out during a performance at one of her Vegas shows in 2017. She was wearing a dazzling green leotard when it happened.
What are your thoughts on Britney's "slip"? Sound off in the comments!