West Yorkshire Police say that the 39-year-old man was sat in his grey Range Rover on Woodroyd Road when at least two suspects approached the vehicle and opened the driver’s door.
They demanded the keys and hit him with what was thought to be a tyre brace after he refused to hand them over.
He had to have hospital treatment for a cut to his head.
The suspects were wearing dark clothing and had their faces covered, they are thought to be in their mid-teens to early twenties and ran off towards Parkside Road.
Witnesses to the incident last Saturday (September 15) at 12.25pm asked to contact Bradford District CID on 101, quoting crime reference 13180460537, or use the live chat facility on the West Yorkshire Police website.