One in three 55-year-olds may have fallen victim to pension fraud within the past three months, according to research.
Based on interviews with 610 private pension holders aged 55 and over, the firm said these consumers were contacted by phone, text or email.
The study, carried out by Retirement Advantage, found one in five were approached with offers of free reviews or investment advice.
Andrew Tully, the firm's pensions technical director, said: "It's a huge concern that many more people are telling us they have been approached by companies offering free pension reviews or investment opportunities. This seems to be the start of a trend so it is crucial people are alert to the possibility that scammers may get in touch."
The pension provider said consumers should stay alert for offers to access pension savings before the age of 55, as this is only possible in "rare situations" such as illness.
It said they should be wary of any recommendation to take a large amount of money or the entire pension pot in a lump sum and invest it, adding: "There are significant tax implications if you take lots of your savings in one go, so check the tax position before you make any decisions."
Retirement Advantage also advised people to take time to choose the right retirement product and urged them to act if they receive any warnings that the "deal is limited".
In addition, it said consumers should be "very suspicious" if they are discouraged from seeking professional financial advice or talking to Pension Wise or The Pensions Advisory Service.
The pension provider also urged people to be aware of those who are not on the Financial Conduct Authority Register - a public record of all the regulated firms and individuals in the financial services industry.
Tully added: "It is clear there are unscrupulous people preying on certain groups, using increasingly sophisticated and convincing ways of trying to defraud large amounts of cash from people's pensions. We all need to be on constant guard; if an opportunity sounds too good to be true, it almost certainly is."