“I love Sushi! Ahhhhhhhhh!” the Blurred Lines hitmaker, 39, captioned the image.
The father-son photo comes days after Thicke got into another legal squabble with his ex-wife Paula Patton in their ongoing custody battle.
“Julian’s favorite food is sushi, and so Robin took him to Nobu and they had a really fun lunch,” a source told PEOPLE of the outing. “Afterwards, they went back to Robin’s house and played sports in the backyard.”
Joined by a monitor, the father-son pair “spent eight hours together and had a very, very good time,” added the source. “He wanted to do something extra special that he knew Julian would love.”
On Feb. 7, Thicke’s legal team requested either “no monitor, a change in monitor or a ruling that said the monitor couldn’t make changes to the visitation” with Julian. The court denied his requests and Patton’s legal team asked for Thicke to have only two nonconsecutive visits per week for no more than two hours per visit. The judge also denied her request.
On Jan. 26, Patton was granted sole custody of their son.
Reportedly, Thick has a history of domestic violence, infidelity and addictions.
The Warcraft actress, 41, has accused the singer of physically assaulting her, cheating on her multiple times and having a serious cocaine problem.