Officers have appealed for information after the man, described as in his 20s, then stole cash and an item of property before leaving.
The incident happened on Saturday evening in the Dalneigh area of the Highland capital.
A Police Scotland spokesman said: “At approximately 10.12pm police received a report from a member of the public about an alleged bogus caller.
“The incident, which occurred on St Valery Avenue, involved an elderly woman who answered her door to a man claiming to be a police officer.
“The man proceeded to walk into the woman’s home and take an item of property without her consent.”
Police said a quantity of money was also taken from the 89-year-old.
The caller is described as approximately 5ft 5in in height, slim to medium build and believed to be wearing navy blue clothing which was possibly in a uniform style.
The spokesman said: “Members of the public are advised to always ask those calling at their homes for formal identification and should not allow anyone they do not know to enter their home.”
The police also advised householders to keep their front and back doors locked, even when at home.
If anyone calls, the spokesman said: “Look through the spy-hole or the window to see who it is.
“If you decide to open the door, put the door chain or bar on first. Keep the bar or chain on while you are talking to the person on the doorstep.
“Ask for and take the time to check their identity card. Call the company they say they are from using the phone directory. Don’t call the number on the ID card as it may be fake.”
Anyone with information about the incident is asked to contact police on 101 or Crimestoppers anonymously on 0800 555111.