The actor, who has been dating Saturday Night Live producer Lindsay Shookus for over a year, was seen leaving Nobu in Malibu, California on Thursday night.
A source tells PEOPLE Affleck, who turned 46 on Wednesday, had dinner solo with Sexton in what “looked like maybe a first date.”
“They weren’t affectionate but seemed to have a fun dinner,” the source says. “He ordered for them and took care of the check. They chatted across from each other.”
The insider adds, “She looked very cute, and he seemed interested.”
The Justice League actor was photographed wearing a green T-shirt, navy jacket and jeans while the model, 22, wore a nude colored bodycon dress.
Sexton is originally from Virginia and was named Miss May 2018.
Affleck spent his birthday with his three children, Violet, 12, Seraphina, 9, and Samuel, 6, whom he co-parents with ex Jennifer Garner.
Noticeably absent from his birthday festivities was Shookus, whom the Oscar-winning director was last photographed with in late July.
Affleck’s latest outing also comes after a friend close to the actor told PEOPLE that he has been in a happy, health-focused place as of late.
“Ben is doing well,” the Affleck pal said. “He is in a good place mentally and has worked really hard to get here. He continues to focus on himself and the health of his relationships.”
The friend added, “He attends meetings, many meetings, and he also does meditation and yoga. While he still has his moments — and let’s be honest everyone struggles — he continues to work hard on himself.”
Meanwhile, PEOPLE previously reported, Buffalo native Shookus has been staying at Affleck’s $19 million mansion on and off, as well as her own place in L.A. for the summer.