"I wanted to celebrate my 21st Birthday with all of you, so we made this video for us all to celebrate to," the singer wrote on the description. "Thank You for all the love and support you have shown and continue to show me. I love you all so much!!"
In the clip, the former Disney star dances around with friends in a black crop top and shorts with a flannel shirt around her waist. At the end of the clip, her pals sing her "Happy Birthday."
Early Monday morning, the "Come and Get It" singer posted a photo of herself and friends on her Instagram account captioned, "Guess what... I'm 21. UM, #turnupNOW."
Gomez's special day comes a few days after the star admitted to Ryan Seacrest that she was no longer with on-again off-again boyfriend Justin Bieber, saying that all she wants in a man is honesty and that "egos turn [her] off."
As for her birthday plans, the star is planing to celebrate like an adult.
"I'll have a birthday party but I'll have a dinner on the actual birthday and I will order my first glass at a restaurant," she said, adding that it would probably be of red wine.