A man entered the Scotmid store on West Main Street in Harthill, around 8.45pm on Tuesday, and threatened staff with a knife and demanded money. He then made off on foot with a three figure sum of money.
The three female staff members were uninjured but badly shaken as a result of the robbery. The suspect is described as white, 6ft of medium build.
He was wearing a black hooded jacket, navy tracksuit bottoms, white trainers, a dark coloured skip hat and a black scarf around his face.
Detective Constable Stuart Wright, of Wishaw CID, said: "We are carrying out inquiries in the local area including house to house inquiries and studying CCTV footage.
"I would urge any witnesses, or anyone with information regarding this robbery to contact Police Scotland on the non-emergency number 101. Alternatively Crimestoppers can be contacted on 0800 555 111, where anonymity can be maintained."