In the adorable black-and-white photo, the "What Do You Mean" singer looked at the girl's eyes while she's staring at the camera, reported Ace Showbiz.
The Bieber was seen wearing a white T-shirt under a baseball outer which he left open.
"My daughter.... Just kidding," he captioned the snap.
It's not clear who the girl is, but it looks like it's their first encounter.
One fan noticed that Bieber mistakenly thought that the baby's a boy. He initially called the baby "my son" before he corrected it. "He wrote first 'my son...Jk' and then changed to 'my daugther.. Jk,' " one fan commented in the comment section.