West Yorkshire Police has today released CCTV images of a number of people they want to identify following the attack.
Also in crime: Man cautioned after 'bricking' claims in BradfordIt happened in a car park in Lower Kirkgate at about 2am on Saturday, June 30.
A spokesman said: "The victim had his bank card, a quantity of cash and two silver chains stolen. He also suffered broken ribs, cuts and bruises.
"The suspects are believed to have run off towards the city centre following the incident."
One robber was described as being white, in his late teens, around 5ft 5in and of medium build, with short, blonde hair. He was wearing a sky blue tracksuit.
Anyone who can help police is asked to contact Bradford District CID on 101, quoting crime reference 13180318215.
Information can also be passed on via the live chat facility on the West Yorkshire Police website or reported anonymously to the independent charity Crimestoppers on 0800 555 111.