The incident took place at the premises in the Melmount Road area shortly after 9.30pm on Friday night.
A masked thief entered an off licence armed with a knife, threatened two female shop assistants and stole a sum of money.
No one was injured in the incident.
The man made off on foot with a sum of money towards the Lisnafin Park area .
The thief is described as being between 5ft 3ins and 5ft 6ins tall and is believed to be in his early twenties.
He was wearing a dark coloured raincoat and black woollen gloves.
A police spokesman said inquiries are continuing and anyone with any information about this incident should contact CID at Strabane Police Station on 0845 600 8000.
Alternatively, information can be passed anonymously to Crimestoppers on 0800 555 111.