The actor-director turned 48 on April 6.
"Happy happy birthday to youuuu! The birthday wish has already come true I'm sure," Pugh wrote over a picture of Braff in action directing from the backseat of a car. "Making a f**king awesome movie and people watching it with friends and family. Thanks for being an awesome director and making such a special set for everyone."
Pugh, 27, didn't let the birthday shout-out stop there. The actress shared two additional slides of Braff directing their film, A Good Person.
"More @zachbraff moments in honour of the big birthday," she captioned a photo of her and the Scrubs star standing on set.
"It's @zachbraff birthday," she captioned the final slide.
Pugh and Braff dated for about three years before quietly ending their relationship in 2022. The pair reunited for A Good Person, a film written and directed by Braff, starring Pugh. In the film, Pugh plays Allison, a woman battling an opioid addiction and the aftermath of an accident.
In March, Pugh spoke with ET, who shared the best part about working with Braff -- who created the character for her.
"Him writing for me, it's a luxury. I've had it in the past where people have written something with me in mind to play that character but I've never had someone write in the way that I speak and the way that he knows that I can push myself," Pugh said of Braff.
"He knows my body of work. He knows who I am. He knows my sense of humor. He wrote it truly with me on every page and, obviously, with Allison on every page, and I came and breathed life into her. It made the whole process -- it wasn't an easy character -- but it made it so much easier stepping in. I cut so many corners. I had already done the work of many months of chatting to him about it."
Braff echoed Pugh's sentiments about working with each other for the emotional film.
"I'm just in awe of her talent and I said, 'I wanna write this for Florence. What I'm writing is really gonna be challenging and she's incredible,'" he recalled to ET.