Posing as an "electricity company" worker, the thief tricked his way into the grandmother's home in Balornock, Glasgow, and stole two purses containing her bank cards and more than £200 she had withdrawn from her bank.
The widow said: "Although I'm upset, I'm just glad he didn't hurt me. It could have been much worse."
Police warned people to be on their guard after the robbery in Broomknowes Road at about 5.20pm on Tuesday.
The woman explained: "The buzzer went and there was a man asking to get into the building.
"He then came to the front door and asked if I had heard about 'the big crash' nearby, but I didn't know what he was talking about.
"Before I knew it, he was inside, saying he was from the electricity company and had to check all my sockets, because the accident had affected some properties in the area.
"He asked me to help, so we went around checking them but, when I think back, we were never in the same room at the same time. He said everything seemed alright, and then he was gone.
"It was only later I checked my handbag and realised he had taken both my purses, one with my bank cards and the other with some money I had taken out to buy Christmas presents."
PC Jamie Campbell of Baird Street police office said: "This is a despicable crime, and it is vital we trace the person responsible.
"We would like to remind people to be vigilant, particularly where elderly neighbours or relatives are concerned, especially at this time of year."
Patrols in the area have been stepped up as the hunt for the man continues. He is described as 25 to 35, white, about 5ft 6in with a thin build, wearing a black jacket and dark trousers and had a Scottish accent.
PC Campbell added: "Residents should never allow anybody access to their home without proper identification. If you are in doubt about a caller, please contact us, and always report anything suspicious."
The pensioner, who was married for more than 60 years before her husband died, added: "I would urge everyone to be careful, and be on guard. Don't make the same mistake I did."
Anyone with information should contact Strathclyde Police on 0141 532 2000.