Like mother, like son...maybe.
"He *might* be getting my dimple," the actor, 41, captioned a carousel of photos of the pair.
In the first photo, Munn and Malcolm both have their hands on their faces, with Munn's dimple on display, and what appears to be an identical dimple forming on Malcolm's cheek.
In photo two, both Munn and Malcolm appear to be looking intently at something off camera, and in the last photo, Munn's hands gently pinch the youngster's cheeks.
Fellow celebrities could not resist weighing in on baby Malcolm's cuteness.
"I can’t Olivia he’s SO yummy and I’m just so happy for your mommyness," entertainment reporter Catt Sadler commented.
Paris Hilton chimed in, "Cutie!"
Fans were quick to share their thoughts on Malcolm's budding dimple.
"He’s going to kill it with all the ladies with them baby blue eyes. The dimple is going to melt them all too," one commenter wrote.
Another added, "And he looks just like you!!! Dimple and all."
It's not the first time Munn, who shares Malcom with partner John Mulaney, has shared updates on motherhood.
In May, the actor celebrated six months of parenthood with a candid mother-son snap.
"I love you so much Malcolm Hiệp," she captioned the photo. "Happy 6 months being earthside with us. You lit up our whole world."