The brunette model has in fact been celebrating her 18th for the last few days, with her older brother Rob even giving her an adorable puppy called Blu as an early gift last weekend.
But for her actual birthday (3 November), the entire family rallied round to take Kendall out for dinner, along with her closest friends.
Khloe, Kim, Kourtney, Kylie and mum Kris were just some of the VIP guests at Kendall's birthday meal and they each donned colourful sequin face mask for the occasion. We know how much the Kardashians love to dress up!
The Kardashian clan also presented their teenage sibling with a stunning cream cake, which was adorned with icing in the shape of roses and had the message 'Happy Birthday Kendall We Love You So Much' written on it too.
Kendall posted a close up snap of the cake and wrote: "it's so prettyyy! I don't even want to eat it".
Her friends were also present at the dinner and they'd made sure to shower Kendall with surprises earlier in the day, by decorating her room with pink trinkets and hanging a birthday banner above her bed.
Of course, the Kardashian sisters were quick to send well wishes to their younger sister with various messages on Twitter and Instagram.
Khloe wrote: "Happy birthday Kendall!!!!! 18 years ago my life was changed forever because of you! The joy and peace you bring to so many lives are just a few of the rare gifts your spirit possess. I couldn't be prouder of the woman you are becoming. Happy birthday to my best friend, my roommate, my puppy sister, my heart. Sisters by blood, best friends by choice."
Meanwhile, 33-year-old Kim wrote: "Happy 18th Birthday to the sweetest girl I know @kendalljenner I hope your adult years are filled with happiness & so much love."
Momager Kris also posted a sweet message for her young daughter, writing: "Happy Birthday to one of the most amazing joys of my life!!! I will never forget how blessed we were the day you were born and I thank God for you every single day!!!! I love you with all of my heart @kendalljenner You are truly a gift ......"
No doubt it was nice for Kendall to be surrounded by her nearest and dearest, since her mum and dad Bruce Jenner announced last month that they have separated and are now living in different houses.
However, despite the couple putting an end to their 22 years of marriage, they have insisted that they will remain best friends and will not be filing for divorce.
What did you do for your 18th birthday? Let us know below, as the best comment each week wins £50!