Halifax District CID are appealing for witnesses to the incident which took place in the car park of the Tesco store on Haugh Shaw road at about 10pm on Friday night.
It occurred after the victim, a 25-year-old man, was approached by two masked men as he walked towards his car.
The men demanded his keys and when he refused to hand them over he was assaulted.
The suspects then made off in his blue Volkswagen Golf leaving the 25-year-old with a serious but none life threatening injury to his arm.
He attended hospital for treatment.
Detective Inspector Helen Madden of Halifax District CID, said: “We are appealing for witnesses to this incident and are carrying out enquiries into the circumstances of what has taken place. Anyone who saw the attack, two men in the car park behaving suspiciously in the moments leading up to it, or the Golf leaving the scene is asked to contact DC 4497 Richard Drabble at Halifax CID on 101. Information can also be given anonymously to the independent Crimestoppers charity on 0800 555 111.”