'The Mentalist' Star Robin Tunney Gives Birth to a Baby Boy -- See the Adorable Pics!

Robin Tunney gave birth to a baby boy!

The 44-year-old actress and her fiancé, interior designer Nicky Marmet, welcomed their first child together last month.

READ: 17 Celebrity Moms Who Gave Birth In Their 40s

Tunney revealed photos of her adorable newborn on Instagram Tuesday, alongside an apology for keeping her pregnancy under wraps.

"My greatest work, Oscar Holly Marmet," Tunney wrote next to a snap of the sleeping baby. "Sorry I didn't talk about being pregnant. Wanted to keep it all for myself #momlife #bestbaby #solinlove."

My greatest work, Oscar Holly Marmet. Picture by my friend @shannonleeimages. Sorry I didn't talk about being pregnant. Wanted to keep it all for myself. #momlife #bestbaby #solinlove

A photo posted by Robin Tunney (@realrobintunney) on Jul 5, 2016 at 1:48pm PDT

WATCH: Why Tyra Banks Hid Her Baby News From Her Closest Friends

The Mentalist star also shared a family photo with Marmet holding Oscar while she holds their dog, Rufus. "First photo of the whole family," she wrote. "Rufus would have preferred we'd gotten another dog."

First photo of the whole family. Rufus would have preferred we'd gotten another dog. #firstmonthofmotherhood #greatestbabyever

A photo posted by Robin Tunney (@realrobintunney) on Jul 6, 2016 at 6:25am PDT

Tunney is among a growing list of celebs to stay mum on pregnancy news. Watch Laura Linney explain why she didn't announce her 2014 pregnancy in the video below.