The Kardashians put their party outfits on display as they celebrated Kendall Jenner’s 20^th birthday.  All were dressed to impress but Kourtney Kardashian was betrayed by her see-through outfit that night.

The reality star, who recently split with Scott Disick, her boyfriend of nine years, came to the party looking sexier than ever. Kourtney showed off her cleavage in a plunging black lacey corset-like top, which she paired with skintight leather pants, a black bomber jacket, and a pair of black pointy-toe high-heeled shoes.

Kourtney Kardashian shows a good deal of cleavage at Kendall Jenner&#039s birthd… – https://t.co/qYfAD8ZK4U pic.twitter.com/I7Jf2RAH6U

— Viral Buzz News (@VIralBuzzNewss) November 3, 2015

The ultra-sexy outfit was made mainly of sheer fabric, which quite easily allowed a nip slip to happen. Was Kourtney not aware of it? Looking at the picture, the reality star was not wearing a bra underneath her super see-through top, which barely covered her breast.  Nevertheless, she seemed to have a lot fun that night as she danced the night away with a male friend. The mother of three was not the only one who flashed some skin that night. The birthday celebrant hit The Nice Guy restaurant in West Hollywood wearing a chest-baring black Sergio Hudson jumpsuit, while Kourtney Kardashian sported a skintight body suit.

Kendall Jenner’s 20th Birthday Party Is Just What You’d Expect It Would Be https://t.co/pXABKtlQVD pic.twitter.com/SCIHpJmzmW

— Cosmopolitan (@Cosmopolitan) November 3, 2015

Kourtney, who has faced a lot of personal issues these past months looked like she enjoyed the party with her family. She posed for the cameras with her sisters, and the newly-single Kardashian looked glowing and in high spirits. In another photo, she flashed a wide grin with Kim, Gigi Hadid, and the Kendall.

Girls just wanna have fun ????

A photo posted by Kim Kardashian West (@kimkardashian) on Nov 3, 2015 at 12:48pm PST

“Girls just wanna have fun,” Kim captioned the black and white Instagram photo.

The day before the birthday bash, Kourtney visited Disick at the Cliffside rehab in Malibu. She and her sister Kylie Jenner brought along Mason, 5, Penelope, 3, and Reign 11 months so Disick could spend a little time with his three children.