A survey of more than 1,000 people aged over 65 highlighted worries such as health and care, as well as having enough money to pay for energy and food.
Age UK said its report showed that affording daily essentials remained a challenge for millions of pensioners living on low fixed incomes.
Caroline Abrahams, charity director at Age UK, said: “We are not surprised that a third of over-65s in our research think Britain has become a worse place to live during the last year.
“Easy headlines about a fortunate minority living on good incomes and in sound health should not blind us to the reality facing considerably more people in their 60s, 70s, 80s and beyond, for whom life is not nearly so rosy and the future a source of constant concern.
“Age UK wants the next government to be ambitious and aspire to transform this country into ‘a great place to grow older’ for every older person today and tomorrow.”
The charity called on the next government to plug funding gaps in health and social care as well as take action to tackle pensioner poverty.