The Oscar-winning actress called for the BBC and the Government to "do the right thing" and reinstate the benefit.
In an open letter published in the Mirror, Dame Helen, 73, said television in many cases "acts as an important contact with the outside world."
She wrote: "I urge all those involved, including the Government, to do the right thing and to carry on funding free licences for all over-75s, the cost of which is surely a small price to pay for keeping so many vulnerable older people connected."
The BBC announced the end of the universal benefit, saying it cannot afford to take on the financial burden from the Government.
From June 2020, the concession will only be made available to households where someone receives pension credit.
The move sparked a backlash, with MPs among those demanding it be reversed.
Dame Helen is said to be one of 20 celebrities who have added their names to the letter, asking the Government to stick to the Conservative manifesto promise to fund free TV licences for over-75s.
Others reportedly include Sir Lenny Henry, Angela Rippon and Amanda Redman.