The 19-year-old "Neighbors 2" star made the revelation on "Watch What Happens Live!".
"I think the more I don't make it mysterious the more people don't care, so yes we're in a relationship," Moretz said.
The actress also praised famous parents of her 17-year-old boyfriend.
"He's a great dad, she's a great mother. They genuinely are very good parents that's what matters most, they made a pretty son," she said.
Brooklyn has been sharing adorable photos of his girlfriend even calling Moretz his "bae". The dating speculations first started back in 2014 when they were spotted hanging out together.