Justin Bieber‘s definitely all grown up and sounding more like Clint Eastwood than a young pop star when some teens in Bev Hills ticked him off in a fancy hotel.

The new clip circulating on social media shows the singer-songwriter Thursday in the lobby of the Waldorf Astoria, a popular celeb hot spot, where he confronted the pack of teenagers.

In the vid, he’s angrily asking the teens what they find so funny — very Joe Pesci from “Goodfellas,” we gotta say — waving them away from him while hotel staff appears to be shooing them out the door.

Witnesses tell TMZ he had good reason to be upset … he was meeting his pregnant wife Hailey Bieber for lunch at the hotel when 8 teens — who were at the hotel for a bar mitzvah — started following him around and yelling at him.

Bieber had limited security and asked the kids nicely to back off at first … but, they kept filming him like a circus animal, we’re told — and JB got frustrated.

Our sources say Bieber didn’t swear at the kids, and he was just trying to get on with his day … and, we’re told he was just worried about his wife’s safety.

As you know … Justin and his wife Hailey are expecting their first child any day now. Sources told us she was six months pregnant in early May. Do the math … we can expect Baby Bieber very soon.

Justin shared a loved-up snap with his better half recently … featuring Hailey’s huge baby bump — so, clearly, everything’s going great in their relationship.