Police said the"courageous"patron also threw a pot plant at the offender when he walked into the pokie machine area and demanded cash during the early hours of Friday.
The crook,who was wearing a balaclava,entered the Mermaid Beach Tavern about 12.45am through the back door and demanded money from a 37-year-old female staff member.
As the employee was about to hand the money over,the patron,a 29-year-old man,attacked.
The offender stumbled backwards and swung the machete wildly,before grabbing the money and preparing to make a break for the exit.
The patron struggled with the robber as he tried to leave,causing the bandit to drop his machete before bolting out the front door with his loot.
However,the staff member and patron caught up with him and wrestled the money back,leaving the criminal to flee empty-handed.
The employee and good Samaritan were not injured.
Detective Acting Senior Sergeant Dane Sheraton said officers were reviewing"very clear"CCTV footage of the incident,taking witness statements and checking for any DNA evidence.
"It was very courageous by him[patron] and I think he should be commended for his actions,"Acting Senior Sergeant Sheraton said.
The offender has been described as aged 45-50,Caucasian in appearance with a large build,balding with brown shaven hair,a large nose and an Australian accent.
He was wearing a black hooded jumper,black track pants and a black balaclava.
Anyone with information should contact Policelink on 13 14 44 or Crime Stoppers on 1800 333 000.