A fast food outlet at Shore Road in Whiteabbey was robbed on Thursday, 3 September.
Police say that a man with a hood up and his face covered entered the premises shortly before midnight, armed with a knife.
He demanded money before making off on foot with a small amount of cash. The man was last seen heading in the direction of Glenville Road.
Detective Sergeant Crothers said officers attended the scene and spoke to the employee, who although was unharmed, was left obviously shaken by the ordeal.
“Our enquiries are ongoing, and we would appeal to anyone to get in touch with any information which may assist – including CCTV, dash cam or other footage.
“Please contact police using our witness appeal form at https://reporting.psni.police.uk/appeals, quoting reference 1809 of 03/09/26, or call us on 101.”
Alternatively, you can call Crimestoppers anonymously on 0800 555 111 or online at http://crimestoppers-uk.org/.