The man went into Costcutter off Wains Road, Dringhouses, at about 9.45am and threatened a member of staff with a knife.
He then stole cash from the till and a bottle of vodka before leaving the store and riding off on a silver pushbike in the direction of Chaloners Road.
The robber is described as white, in his thirties, and wearing a black face covering, dark coloured clothing and a baseball cap.
Police have released a CCTV image of a man they want to talk to.
Detectives are appealing for anyone who recognises the person in the image to contact them, as they believe they may hold important information.
Detective Sergeant Mike Holden from the York and Selby Investigation Hub said: “We realise the CCTV image may not be of the best quality, but we’re hoping it jogs a witness’s memory, who may hold that vital piece of information which would enable us identify this individual.
“We’d also like to speak to anyone else who was in the area at the time of the incident, who may have seen someone matching the description either enter the store or leave the area on a bike.
“Similarly, any local residents who captured CCTV or doorbell footage, or motorists who may have dashcam footage of any suspicious activity in the area are also asked to make contact with police.”
Anyone with information can email [email protected] or contact 101, select option 2 and ask to speak to Detective Sergeant Mike Holden.
Crimestoppers can also be contacted anonymously on 0800 555 111.