Abdou Cisse, 46, tried to calm the brawl between two people outside the Drunken Monkey, 1207 Forest Ave., about 3:40 a.m., but was knocked to the ground and cracked his skull, the NYPD said.
Cisse, who lived in Mariners Harbor, was pronounced dead at the scene, police said.
"He was not just a customer, but a gentle giant that I loved," tweeted Angela "Big Ang" Raiola, who owns the bar and stars on the VH1 reality-show "Mob Wives."
Raiola, the niece of the late head of the Genovese crime family, opened the bar in 2007.
"I personally share my heartfelt condolences to his loved ones, and we too are feeling this loss in our drunken monkey family," Raiola added.
Cisse, who was originally from Senegal, was remembered by neighbors as a friendly man who was always willing to help out.
"He's a really nice guy," said Joseph Cwick, who lives next door to Cisse on Richmond Terrace. "I can't say nothing bad about him. He helps out everybody on the block."
The two people who were involved in the fight managed to flee and were still at large Monday morning, police said.