Two-fifths (40 per cent) of those aged 46 to 55 do not know how much money they have saved in their pensions, Aviva found.
People in this age group are more likely than younger workers to have lost track of how much they have in their pension savings, with 24 per cent of employees aged 22 to 30 saying they do not know how much they have put away.
This is despite the launch of the pension freedoms in 2015, which give over-55s with a defined contribution (DC) pension pot a wider range of options over how they can use their money.
Alistair McQueen, head of savings and retirement at Aviva, said: “Not knowing how much you have saved in your pension pots is like approaching retirement with a blindfold on.
“For those in their 40s and 50s, understanding retirement savings is especially critical.
“They can be accessed at age 55, at which point some big decisions might need to be made.
“Without knowing how much you have saved it’s difficult to put a plan in place that could improve your retirement.”
Under the pension freedoms, over-55s are no longer required to use their pension pots to buy an annuity retirement income.
They can now cash in their pot, take some of it, or leave it invested - or still buy an annuity if they want to. There will also be tax implications to consider when people are weighing up their options.
The survey among more than 2,000 employees aged 22 to 65 found nearly a third (31 per cent) across this age range admit to not knowing how much they have saved in their pensions.
Nearly half (49 per cent) believe they need to be saving more.
Workers aged 31 to 45 - many of whom will be dealing with the financial pressures of raising a family - are the most likely to say they need to increase their pension savings.
Across the survey, 42 per cent of workers feel secure, confident, proud or excited about their savings - a percentage nearly matched by the 41 per cent who feel worried, disappointed, stressed, regretful or panicked.
In terms of the emotions people attach to their savings levels, people are most likely to say they are worried - with 18 per cent agreeing with this - although this was closely followed by 15 per cent saying they feel secure.
Women are much more likely than men to be worried about their savings levels - with 23 per cent of women saying this compared with 13 per cent of men.
Giving his tips on how people can get to grips with their pension pots, Mr McQueen said: “For anyone who doesn’t know how much they have saved in their pension, now is the time to check.
“If you’ve had a few different jobs over the years then you may have money saved in different pension pots. If you don’t know the details of them then the government’s pension tracing service is a good starting point (www.gov.uk/find-pension-contact-details).
“Once you have your pension details and know how much each is worth there are a range of options available, including consolidating them into one place to make them easier to manage.
“It’s worth considering financial advice at this stage as it’s important to understand any guarantees or charges that different pensions carry.”
A Department for Work and Pensions spokesman said: “Our reforms have transformed pension saving in this country and we are committed to ensuring people are supported to plan ahead.
“Automatic enrolment has boosted the pensions prospects of almost 10 million people so far, setting them on the path to a financially secure retirement. We know there is more to do in terms of increasing contribution rates, and a further rise is due in April.”