The Government is being urged to promote the benefits of volunteer work as people approach their retirement.
The call from the Royal Voluntary Service followed research suggesting there was potential to increase the older volunteer force by half a million in the coming years.
A survey of more than 1,000 people over the age of 55 found that half do some form of voluntary work.
Britain's ageing population gives an opportunity to increase the number of volunteers, said the charity.
It urged the Government and employers to promote the benefits of volunteering.
David McCullough, chief executive of the Royal Voluntary Service, said: "Older people have so much to offer; their experience, skills and talents would be worth a fortune in the job market yet many choose to be generous with their time and volunteer.
"Sadly we are failing to realise and harness this talent as much as we could.
We need to do more to motivate older adults to volunteer which will provide the help that is so desperately needed and at the same time, will give them an opportunity to meet new people and to remain active and engaged in their local community.
"Volunteering in retirement should be normalised so it becomes a little like work experience for young people; a must-have part of their post-work plans.
"It's vital to engage older people before they leave a company and, to achieve this, the voluntary sector needs to work with Government and businesses to convince future retirees to include volunteering when planning the next phase of their life."
Lisa Harris, of Saga, said: "The over-50s really are the generous generations and it's right that we all do more to help raise awareness of the volunteering opportunities available to them.
"For many, as they start the process of working towards retirement, they choose to give a little of their spare time to volunteering."