SunLife polled 50,000 individuals and found that 2 in 5 over-55s worry about whether their pension will cover retirement, while 43% are concerned they might run out of money before they die.
This strain on retirement income was also shown to impact living standards, as a fifth of respondents felt they were financially worse off than they expected to be.
Separate research by the Institute for Fiscal Studies (IFS) shows that many people may not be adequately estimating the years of retirement income they will need to plan for.
The data shows that those in their 50s and 60s tend to underestimate their chances of living through their 70s and 80s.
This could mean those individuals save less during their working life and spend more earlier on in retirement, the IFS warns.
Dean Lamble, chief executive of SunLife, said:
In some ways, there has never been a better time to retire – we’re living longer, enjoying healthier, more active lifestyles, and thanks to the new flexible rules around pensions, we have more freedom to spend our pension savings as we choose.
But with the average pension pot of someone over 55 around £105,000, people are clearly worried that they haven’t got a big enough pension to fund their retirement.