The 55-year-old actor was spotted sporting a cheeky smirk while out and about near his home on Valentine's Day, and it looked as if Brad literally couldn't wipe the smile off his face.
The Inglorious Bastards star cut a casual figure in a black zip up, loose grey t-shirt and black pants.
Brad donned a battered pair of grey sneakers with a gaping hole in the right shoe and carried a patterned bucket bag over his shoulder.
Attempting to go about his day incognito, he wore his trademark paddy cap and a large pair of aviator sunglasses.
The usually aloof actor shot cameras a knowing grin leading fans to speculate about the cause of his chirpy demeanor.
Rumours of a romantic reunion between the friendly exes have been swirling since Brad made a surprise entrance at Jennifer's low-key pre-birthday bash and later attended the main event at Hollywood's Sunset Tower Hotel.
An insider close to Jen revealed that "Ellen [DeGeneres] and Portia [de Rossi] arranged an intimate pre-birthday dinner for Jen at West Hollywood's Soho House for a group of 12 close friends in a bid to get Jen excited about her big birthday and to cheer her up.
"They'd just ordered some drinks when Brad walked over to the table and Jen nearly fell off her chair when she realised it was him - bursting out in tears it was clear all the emotions of the past few months had finally come to a head," the source added.
As for birthday gifts, Brad reportedly helped Jen ring in her half century with "a card, a hug and a kiss".
A source revealed to In Touch magazine: "He slipped her a birthday card... they hugged and kissed and insiders say they met up afterwards."
The source continued: "They chatted and it didn't look awkward at all."