Police are appealing for witnesses following the incident at the One Stop shop on Church Road, in Altofts last night.
It happened at around 10.25pm, when the suspect entered the store and threatened a member of staff with a knife and demanded money.
The suspect, who was wearing all back and had their face covered, then made off with a quantity of cash in the direction of Altofts Hall Road.
No one was injured in the incident and enquiries remain ongoing.
Anyone who witnessed the incident or saw any suspicious activity in the area is asked to contact police by calling 101 and quoting crime reference 13190015994.