The 46-year-old actor and 54-year-old actress came together to attend 14-year-old daughter Coco's high school play, according to E! News.
Arquette shared a family photo with Cox and Coco following the production. He couldn't help but gush about his daughter in the caption.
"I'm so proud of my daughter Coco! Have fun and be safe in Highschool! AND don't grow up too fast! I love love love you!!!" the star wrote.
Arquette and Cox split in 2010 after 11 years of marriage. The actor reflected on his relationship with Cox in a Facebook Live interview with Yahoo! Entertainment in February.
"I met my first wife and we had a kid together during that whole experience," Arquette said of the movie Scream and its sequels. "In the final [film], we got separated."
"We had a relationship where I was kind of the fun crazy one, although she's really fun and somewhat crazy as well. But she was going through a renaissance too," he added.
Arquette got remarried in 2015 to Christina McLarty, and is parent to two sons, 4-year-old Charlie and 17-month-old Gus, with the former TV reporter.