The sale was completed without face-to-face contact, using emailed or posted documents, ABC News reports.
The original owner, who is based in South Africa, had been treating the house at Macgregor as an investment property and was renting it out.
They only discovered the fraud when they contacted the real estate agent to question why rent payments had stopped.
Now the original owner will have to challenge the new buyer in order to win back title ownership.
Depending on the outcome, either the owner or the buyer will have to pursue the money lost through the completed sale through legal channels overseas.
ACT police said it is investigating the case and all local real estate agents have been sent a checklist to follow when overseas owners ask via email for a property to be sold.
Real Estate Institute ACT chief executive Ron Bell said agents should be wary when business is done by written communication only.
“People should verify signatures and verify the material that has been given to them and they can do that through any [Australian] Embassy that is overseas,” he was quoted as saying.