Phoenix welcomed a son with his fiancee Rooney Mara last September, and the couple named him River honour of his late brother.
Joaquin Phoenix, actor Gaby Hoffmann and writer/ director Mike Mills attend the photo call for 'C'mon C'mon' during the 59th New York Film Festival. Photo / Getty Images
Phoenix plays radio journalist Johnny in C'mon C'mon, directed by Mike Mills. Woody Norman plays Jesse, Phoenix's character's 8-year-old nephew in the black and white film.
Gabby Hoffman stars as Johnny's sister Viv, and was snapped next to Phoenix.
"I get to compliment Joaquin, which he hates, this is rad," Mills said on stage at the event.
"To me, Joaquin did so much more than be this character. I feel like I made this whole film with this person and I couldn't have done it without him. He is my great friend and comrade. His support, faith, and excitement made it happen. So thank you, sweetie."
The actor had originally shaved his head bald for Ari Aster's film Disappointment Blvd.
Michael Gandolfini and Amy Ryan are among the cast members, however not many more details have been released about the A24 film.
