Kylie started off Friday at Children's Hospital Los Angeles, donating gift bags to patients.
"Let the birthday celebrations begin," the Keeping Up with the Kardashians star wrote on Instagram while standing in front of her cartload of bags.
Then, on Friday night, Kylie met up with her family members at Nobu in Malibu for dinner. The gathering included a public reunion between her divorced parents Caitlyn and Kris Jenner.
Kylie, who was gifted a highly sought-after Hermés Birkin bag during the party, posed for a series of selfies with sisters Kourtney Kardashian, Kim Kardashian West and Kendall Jenner.
"Sistersquad," Kim wrote on Instagram. Kourtney shared one of the photos on her own account, as well, re-captioning it "squad goals." The sisters also posed with Caitlyn.
"The festivities are just beginning," Khloé wrote of a photo of Kylie with a frosting-heavy, heart-topped cake. "My baby girl is going to be 18!!! I'm legit going to cry."