The former couple adorably sported name tags around the event with two of their three children.
Ben Affleck and Jennifer Garner are supporting their kids.
The former couple both turned up at an elementary school end-of-the-year party in Santa Monica, California, on Thursday.
An eyewitness tells ET that the two arrived and left the event separately, with Affleck staying for about an hour and Garner staying about 30 minutes longer. The parents to 11-year-old Violet, 8-year-old Seraphina and 5-year-old Samuel were not seen saying goodbye to each other.
"Jen did not seem to be in a rush," the eyewitness reveals. "Ben and Jen were near each other outside of the event, but Jen was mainly socializing with other parents and people there."
According to the eyewitness, the 45-year-old actress was seen "enjoying herself, very happy, chatty and relaxed," while her estranged husband "was a bit serious." "Ben has not shaved and it looked like he had stains on his shirt," the eyewitness says.
Both Garner and Affleck adorably sported name tags to the event, which they attended with Seraphina and Samuel.
Last month, Affleck revealed that he "would love to" direct Garner in an action film.
"I think that would be great. I've often said that I want to direct a movie that Jennifer was in because I think she's so great and she could do something really cool," he told People.
"The problem that gets in the way is that one of us has to be looking after the kids at home," he added.
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Reporting by Kayley Stumpe.