The 36-year-old Oscar winner headed to the post office Tuesday in L.A. with baby Jackson in tow.
Dressed in black and sporting oversized sunglasses, the first-time mom carried her newly adopted infant son in his car seat, shielding him from the sun with a white blanket covered in red stars.
So has life completely changed for Theron now that she's a mom?
"It's changed a tiny bit," she told Ryan Seacrest on his KIIS FM radio show. "I now travel in a pack."
"Look, it's been amazing the amount of emails and congratulations," she gushed. "Everyone's just been so lovely. So it's been really nice."