The reality TV star posted a picture of model Kendall looking particularly gorgeous along with the message, "To the sweetest girl in the world Happy Birthday I love you so much @kendalljenner."
Kendall, who appears alongside the rest of her family in reality show Keeping Up With The Kardashians, also received a birthday message from sister Khloe, who uploaded a funny clip onto Instagram and wrote, "Oh I think @kendalljenner is excited #HappyBirthdayKendall #NoFlexZone."
The birthday girl spent much of the weekend celebrating and Instagrammed several pictures of herself partying with friends, including model Cara Delevingne.
Kendall's modelling career has gone from strength to strength in the past year and she has become almost as well known as her older sister Kim.
However she has previously admitted that she found it difficult growing up in Kim's shadow.
"It's hard when your sister is perfect at all times and is just like naturally beautiful," she said.