Terrified punters at the Wheatsheaf pub in Tooting had to run for cover after a drinker started throwing pint glasses and bar stools at fellow customers.
Trouble started just after 10pm on Saturday night when two men started brawling in a private party at the pub, on the corner of Trinity Road and Upper Tooting Road.
The two men were separated by customers and one, who is thought to have started the fight, was ejected after a long struggle with the bar manager and a barman.
Witnesses described the man re-entering the pub, which did not have security and the pair squared up again.
Chloe Lambert, who was in the pub with friends, said: "I was really freaked out. But then he ran back and everyone started screaming.
"Then the guy picked up a pint glass and lobbed it into the group of people. The manager again got him towards the door but he then started picking up bar stools and threw it in my direction.
"The guy was completely crazy. Lots of people had been hit by showering glass and seemed to be bleeding."
A spokesman for Wandsworth Police confirmed they were called to the Wheatsheaf after the fight and arrested two men.