Police say that at around 12.30 am a female staff member was closing the bar when a masked man, armed with a hurley bat, shoved her and demanded money.
He made off with a sum of cash.
The staff member, a woman aged in her 30s, was not injured in the incident but was left shaken.
The man is described as being approximately 6ft tall, of slim build and was wearing a balaclava, dark clothing and white trainers.
Detective Inspector Cummings said: “I would appeal to anyone with any information about this incident to contact detectives at Lisburn Police Station on the non emergency number 101.
“Or if someone would prefer to provide information without giving their details, they can contact the independent charity Crimestoppers and speak to them anonymously on 0800 555 111.”