Some 15% of those surveyed said they are helping the young generation with costs such as university expenses and buying or renting a home, a survey for Investec Wealth and Investment found.
Almost half (47%) of grandparents who give financial help said the money goes towards paying down their grandchild's debt or helping them deal with high day-to-day living costs.
The typical amount that grandparents said they were paying out to their younger relatives was £2,496.
Older people living in Wales were found to be the most likely to be giving their grandchildren a helping hand, with one fifth (21%) of people surveyed there saying they did this.
Youngsters in Scotland were also among those more likely to be receiving help from the bank of granny and grandpa, as were those living in London, the Midlands and Yorkshire and Humberside.
Nick Gartland, senior financial planning director at Investec, said: "We have a number of cases where a grandparent's son or daughter has lost their job and they have had to provide significant financial help to ensure their grandchildren don't lose out.
More than 1,000 grandparents took part in the survey last month across Britain.