Detectives said the fraud started on March 25 when a black man approached the 45-year-old victim in the BD7 area and offered to buy his Nissan Qashqai car.
The victim exchanged details with the man and agreed to meet him at a business park in Canal Road on March 29.
At the meeting, the victim was offered 'gems' which he was told were worth around £40,000 and would need to be sold to get cash to buy the car
The victim agreed to buy the items for a discounted price and thousands of pounds were handed over.
The gems, which were referred to as 'Blue Gold' have been found to be fake and police are now warning the public to be aware of this scam.
Police Constbale Toni Hinnells, of Bradford District CID, said: "While we are only aware of one report of this type of fraud so far this year, we are aware that a similar scam has previously operated in the Bradford and Huddersfield areas.
"It is possible that these men are part of a larger group, who are targeting individuals to gain significant amounts of cash through deception.
"We want people to be fully aware of the potential tactics being used by these criminal enterprises and to report those behind it.
"If it appears too good to be true, it is most likely that it is."
Anyone who has information about this incident or who can identify these men is asked to contact Bradford District CID, quoting crime reference 13170144170.
Information can also be given anonymously to the independent charity Crimestoppers on 0800 555 111.