The model shared a sweet Instagram post on Saturday that showed her holding up balloons that read "25" while posing with Zayn and her sister Bella Hadid.
Bella cutely commented, "Slideeeee to the left. slideeee to the right…Criss cross!!"
Earlier in the day, Gigi posted a series of shots from her big day — one of which shows her and Zayn hugging.
"Had the sweetest day celebrating my 25th birthday with my quarantine family, who made it so special for me, along with all the love I felt from all over the world!" she wrote alongside the images. "Thank you to everyone for the birthday messages, I carried you with me yesterday!!"
She continued, "I am grateful and lucky that my family and friends -near and far- are healthy and safe, and although I missed loved ones I wish I could have celebrated with, know that these times will make us even more grateful for togetherness to be had in the future ! I will never forget my 25th bday!"
Among the photos was a video from "Cake Boss" star Buddy Valastro, who made a cake in the shape of a bagel for the model.
"The icing on the perfect quarantine bday was finding out my surprise everything-bagel-cake was made by the one and only Cake Boss @buddyvalastro who I have watched for over a decade. I CRIED REAL TEARS! BUDDY! This is a dream come true," Gigi wrote. "I can't believe you made this cake for me while the bakery is closed. It means more to me than you know, and when we hopefully meet some day you will truly know that there almost isn't an episode I've missed. 10/10 would be a Carlo's intern whenever needed. 😆 Grateful, honored, your biggest fan."
While Buddy was the man of the moment for Gigi on her birthday, Zayn has been her man for years — well, off and on.
The couple began dating in 2015 but split three years later. They quickly got back together, but they split again in January 2019. Multiple media outlets reported they got back together in late 2019.