Only 47% of people knew how their pension investments were performing, a survey by Opinium on behalf of Hargreaves Lansdown found.
Men were more likely to know than women, at 58% compared to 36%.
Awareness was roughly the same for those aged 18 to 34 and those over 55, with about half in both groups knowing how their pension was doing.
For people aged 35 to 54, just 43% understood the performance of their pension investments.
Of those in the dark, 20% said they did not know what to look for, 18% did not know they needed to check, and 15% did not know how to check.
Clare Stinton, head of workplace saving analysis at Hargreaves Lansdown, said: “More than half of people (53%) don’t know how their pension investments are performing – and the picture becomes even starker when viewed through a gender lens.
“Just 36% of women are in the know, compared to 58% of men.
“This gap in awareness is present across the age spectrum, and it matters, because investment performance is one of the biggest drivers of pension growth.”
Stinton added: “The gender pension gap doesn’t happen overnight, it builds over a lifetime, due to career breaks, the gender pay gap, and more women working part-time.
“Understanding your pension and taking early action can narrow the gap.
“Supercharging contributions in your 20s and 30s, paired with checking in on how your investments are doing while you have decades ahead, can deliver powerful long-term results.”
She said: “This is thanks to compounding – earning returns on your past returns – which steadily does the heavy lifting for you over time.
“If you’re comfortable with the level of risk, staying invested for longer gives you more time to ride out any dips and benefit from long-term growth.
“Put simply, the earlier you start, the more potential you can unlock.”
She added: “Only 43% of those in the sandwich years, aged 35-54, know how their pension is performing. It’s a life stage filled with competing priorities, many will be juggling careers, children, and caring responsibilities.
“Yes, life is busy, but carving out time to invest in you and your future is crucial.
“This is the prime time to take back control and make sure that when the time comes, you’re the one choosing when to retire, how to spend your time, and what kind of lifestyle you want to enjoy.
“Wait too long, and your options may start to narrow.”
Stinton noted that half of 18-34 year olds knew how their pension was performing, with those over 55 only slightly ahead.
She said the main barriers for those who did not know were not knowing where to look or how to check performance, and that nearly one in five did not realise they should be checking at all.
Stinton added that this highlights the importance of financial education, and said more must be done to help people take control of their finances.
She explained that HL Workplace had seen people become more engaged when they received financial education alongside their auto-enrolment pension.
Additionally, Stinton said that roughly a quarter of men and 15% of women chose investments outside the default fund, but these numbers increased significantly when people had the chance to speak one-on-one with an expert.
She said: “People now have more control than ever over their retirement. But they need the right tools, support and confidence to make informed decisions.
“The FCA’s Value for Money framework is a vital step in the right direction, helping protect those sleepwalking toward retirement from underperforming schemes.
“The push to equip providers to offer more personalised support through the advice guidance boundary review is equally important.
“We need to help people join the dots between today’s decisions and tomorrow’s financial freedom.”