Emergency services were called to the club on MacArthur Avenue shortly before 4am and found a man suffering stab wounds to his chest and side.
Bankstown Police have been told a patron had been excluded from the club, before returning and allegedly threatening a security guard with a knife.
A witness went to the assistance of the guard and was allegedly stabbed twice.
The armed man was wrestled to the ground and held until police arrived.
A 73-year-old man has been taken to Bankstown Police Station where inquiries are now underway into the incident by detectives.
The injured man was treated by paramedics before being taken to hospital in a serious but stable condition.
Anyone with information about this incident is urged to contact Crime Stoppers: 1800 333 000 or nsw.crimestoppers.com.au.
