Their relationship has hit headlines in recent weeks, but Kylie made sure any attention was fully focused on her structured black cut-out sheer panel dress as she posed up a storm for photographers.
The Keeping Up With The Kardashians star cut a glamorous figure as she arrived at the party, and 'Rack City' rapper Tyga dressed smart for the celebration in a dark grey suit.
Their appearance follows a recent confession from Kylie's mum Kris Jenner that she has no idea if her daughter and Tyga are still an item.
"I have no idea," Kris said during a radio interview on SiriusXM. "I really don't know. Things at my house happen on a daily, anything is possible. I love Tyga, he's great. He's the best."
Kylie and Tyga were at the centre of split reports two weeks ago, but Kylie confirmed they were still dating during an interview with Ellen DeGeneres.
The 18-year-old said: "Honestly, people have it all wrong. We're not broken up. We just... honestly. We became best friends before anything happened, so I think that's awesome and we're just like, I don't know, hanging out. Living life."
Last week it was reported that Tyga has moved out of her home in Calabasas after they decided living separately would be better for their relationship.
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All you need to know about Kylie Jenner: