It happened in the Cavehill Road area of Belfast on the evening of Monday, 8th September.
Detective Constable McCoy, Tennent Street CID, said: “It is reported that at approximately 11.55pm, two unknown males wearing dark clothing and balaclavas entered a commercial premises.
“They demanded money from the till before one of the males punched a 19 year old male staff member several times.
“The two men then made off towards the Westland Road area with a sum of cash.
“We area aware that another robbery took place at the premises of the same commercial franchise on the Doagh Road in Newtownabbey at roughly the same time, and we are making enquiries into the possibility that these incidents may be linked.
“I would ask anyone who witnessed this incident or who has any information to contact Detectives at Tennent Street 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,” he said.