"Thank you Mommy & Daddy for making me a Oma, I love every minute of it," she added.
Malik confirmed the news that his daughter was born on Wednesday, September 23. "Our baby girl is here, healthy & beautiful," he wrote on Twitter, alongside a cute snap of his daughter holding his hand.
"To try put into words how I am feeling right now would be an impossible task, the love I feel for this tiny human is beyond my understanding. Grateful to know her, proud to call her mine, & thankful for the life we will have together x," he shared.
For her part, the model shared another picture of their tot on Instagram. "Our girl joined us earth-side this weekend and she’s already changed our world. So in love," she wrote.
The Real Housewives of Beverly Hills alum was eagerly awaiting to welcome her first grandchild into the family.
Last month, she posted a photo of herself hugging her daughter's baby bump. "Waiting patiently for her angel to be born," she wrote.
"Of course we are so excited," she told RTL Boulevard in April. "I'm excited to become a Oma in September especially after I lost my mom so recently. But this is the beauty of life: One soul leaves us and a new one comes in, we feel very blessed."
The blonde beauty and the former One Direction member have been in an off-again, on-again relationship for the past four years after Malik called it quits with Little Mix's Perrie Edwards. Malik and Hadid broke up last year and then reunited in December 2019. Prior to getting back together, Hadid had a short fling with Tyler Cameron.
The couple have been staying in their Manhattan penthouse and kept the pregnancy news on the down-low over the summer.
In July she explained in an Instagram Live with V Magazine, that their choice to start a family was “not the most important thing going on in the world.”
“I felt that it’s not really something that I need to share apart from with my family and friends,” she said. "Obviously a lot of people have lost lives due to the coronavirus that was in the beginning of quarantine and still happening."
"And then we moved obviously into the reemergence of the BLM Black Lives Matter movement, and I thought that our presence on social media should be used for that," she said.