Goodbye teen years! Brielle Biermann is officially 20. And to celebrate the big occasion, her Don't Be Tardy mom, Kim Zolciak-Biermann, gathered up her pals and threw her a surprise birthday party in L.A., which was not only attended by her family, but also her friends Malika Haqq, Khadijah Haqq McCray, and Todd and Savannah Chrisley.

Brielle looked pretty shocked that everyone gathered in secret in her honor.

Eventually she pulled it together long enough to blow out the candles on her towering cake.

Prior to the party, Kim headed to Instagram to pay homage to her not-so-little girl in a touching post: "I just can't believe it was 20 years ago today I became your mom! Scared out of my mind yet so excited! Had I known how easy it would have been to raise you I certainly would of had a lot less anxiety! I'm extremely proud of the leader you are, the heart you have and share, the love you have for your siblings, the respect, loyalty, and commitment to your family and above it all how you always have remained TRUE to you!! Keep shining!!!"

Check out some throwback photos of the birthday girl, below.