The men turned up at the pensioner's house in Carluke, South Lanarkshire, at about 12:30 on Wednesday, offering to carry out repair work at his home.
After agreeing to the work, the man paid the conmen in cash but they made off without carrying out any repairs.
One of the men was white, aged 50 to 59, about 6ft tall, of heavy build and spoke with a Scottish accent.
The other man was white, about 5ft 8in, and of slim build.
It is believed they may have used a small white van.
Det Insp Kevin Jamieson, of Police Scotland, said: "These people are the scourge of society who prey on the elderly or vulnerable for their own gains.
"My officers are currently reviewing CCTV footage and carrying out door-to-door inquiries to glean any information about these two men who are responsible for this despicable crime."
He asked anyone who had seen two men matching the descriptions, a white minivan or anyone who may have had the conmen knocking on their doors, to come forward with any information.
"I understand that victims find it difficult to come forward but these people are very expert conmen who can appear to be genuine tradespeople as they can talk in detail about repairs required to properties," Det Insp Jamieson said.
"I must urge people to be on their guard when answering the door to people purporting to be genuine workmen.
"To prey on vulnerable people and defraud them of significant sums of money is appalling and I will do everything to find those men responsible."
A 91-year-old man has been conned out of a four-figure sum of money by two bogus workmen.