"Hanging with my little guy #inlove," Brewster wrote.
And they do look totally in love!
In the adorable black-and-white snapshot, mom and son are sharing an eskimo kiss while making eye contact.
Julian looks very fashionable, wearing a beanie with different types of puppies.
The the Dallas star and her producer husband Andrew Form recently welcomed Julian via surrogate.
"The parents are overjoyed," the Fast and Furious star's rep told E! News.
This is the first child for Brewster and Form, who married in 2007, a couple of years after meeting on the set of The Texas Chainsaw Massacre: The Beginning.
The couple are also proud parents to Labradors Henry and Ella, as evidenced by what Brewster wrote on WhoSay recently, "road tripping w babies #labordayweekend," and posted a pic of the dogs in the back seat.