Over half of all investment scam cases were reported by customers aged 65 and older in the first half of this year, according to Bank of Ireland data.
The bank says older customers who have spent years building their savings are being deliberately targeted by fraudsters.
The most common scams are on social media or start with an ad on an online platform.
They usually look like they are promoting some kind of scheme, or it could be a realistic, yet fake, ad for comparing bonds and deposit rates.
Often they will ask you to leave your contact details such as your phone number and email address.
The head of Financial Crime at Bank of Ireland, Paul O'Brien, warns the phone calls may be from somebody who sounds very professional.
"They'll call themselves call themselves, an investment advisor or an investment strategist. They'll have brochures, they'll have websites, and it can be quite convincing," said Mr O'Brien.
He said older customers are being targeted as fraudsters see them as having the highest disposable income or people who have money to invest.
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"We wouldn't see it in terms of somebody being less careful or not watching out for things," said Mr O'Brien.
"In really simple terms it's just that your average 25-year-old doesn't have €20,000 to invest, whereas maybe an older demographic might have an inheritance or a retirement fund," he added.
When it comes to younger victims, they may be targeted with crypto investments or 'buzzy' tech related schemes that sound too good to be true.
"You have to be really, really careful of those. Definitely, if it sounds good to be true, it definitely is," he said.
"But sometimes they don't sound too good to be true, they'll just be good enough to draw you in. So again, be careful of those as well," he advised.
Anyone who suspects they have been a victim of fraud should contact their bank immediately so that the bank can try to stop the fraud and try to recover funds.
