The unidentified journalist met Smith on the red carpet at the event, kissed him on the cheeks, then attempted to smooch the actor on the lips before Smith pushed him away and hit him lightly across the face.
"What the hell's your problem, man?" Smith said, adding to people nearby, "He's lucky I didn't sucker punch him."
Smith continued to greet fans and answer questions from other members of the media, TMZ said.
The father of three children is married to actress Jada Pinkett Smith.