A Perth man has fallen victim to an overseas scam after his house was sold without his knowledge.

Roger Mildenhall's investment property, worth almost $500,000, was sold in June after scammers emailed his real estate agent saying he wanted to sell, even producing duplicates of the deeds to the house.

Mr Mildenhall lives overseas and returned to Perth last week to find a second property he owned was also about to be sold, but the sale was cancelled.

He has hired a lawyer to try to get his other property back.

The Real Estate Institute's West Australian (REIWA) spokeswoman, Anne Arnold, says agents need to be vigilant.

"It is increasingly going online and you have investors who own properties from abroad and they own properties in WA and you are reliant on email," she said.

"It is a really important message that you need to be doubly careful if it's overseas."

She says changes may have to be made to prevent future scams.

"The Real Estate board and REIWA would look at the need for agents to do a little bit more work around identity, but it does raise a lot of implications for agency practice so I guess we've got to think about that," she said.