The 28-year-old singer confirmed his romance with Hadid in the Instagram tribute Tuesday following reports he and the model are back together.
The slideshow features a video and several intimate photos, including pictures of The Weeknd and Hadid kissing. The post had received over 1.2 million likes as of Tuesday morning.
"happy birthday Angel," The Weeknd wrote, adding red and black heart emojis.
The Weeknd and Hadid split in November 2016 after two years of dating, but sparked reconciliation rumors in April following the singer's breakup with Selena Gomez. E! News confirmed in July the pair were dating again.
"Abel realized once he started dating around, that he actually is still in love with Bella, and they reconnected," a source said.
"Things have been going really well," the insider added. "They have been inseparable and have been truly working with each other's schedules to make it work."
Us Weekly reported this month The Weeknd and Hadid are "fully back together."
"They're doing well and just keeping things low key," a source said.