The Charity Commission and Pro Bono Economics survey findings revealed that 8% of trustees were from ethnic minority backgrounds, compared to 17% in the general population, and 92% of trustees were white.
The findings comes from its largest-ever survey of charity trustees in England and Wales.
The survey found that there were slightly more black trustees under 60 (7%) than in the general population (5%), but that people of Asian heritage made up 1% of trustees compared to 4% in the older population.
The research also showed that most trustees spoke highly of their experience, with eight in 10 saying they would recommend the role.
Around six in 10 said the role let them make a positive difference, and four in 10 (38%) felt more fulfilled because of it.
57% of trustees under 30 said the job helped their career, while older trustees said it gave them a chance to give back.
The research found that most trustees (95%) believed they understood their duties and felt qualified for the job, but many boards still relied on outside help for legal advice.
Most trustees (59%) reported strong finance skills on their board, though finance was also a common area for external support.
Fewer than a quarter said their board had skills in anti-fraud, campaigning or marketing.
The latest data also suggested some change in gender balance, with women now making up 43% of trustees, up from 36% in 2017.
Smaller charities had a higher proportion of female trustees.
Over half of trustees were retired, much higher than in the general population, and only 8% of trustees were aged 44 or under, while just 1% was under 30.
David Holdsworth, CEO of the Charity Commission, said: “This rich and detailed research gives us valuable new insights into the people on whom all charities, of all sizes, ultimately rely.
“This research shows what those of us who have been trustees already knew – that whilst it is a significant responsibility, it is also a hugely rewarding way to have an impact on something you care about.
“I hope that in making these findings available, we can support the sector to respond, encouraging and inspiring a pipeline of committed and skilled people willing to serve as volunteer trustees into the future – and to reap the personal rewards of the role.”
Anoushka Kenley, head of social sector at Pro Bono Economics, said: “This new research provides plenty of room for optimism, with the vast majority of trustees saying that they find their role rewarding and evidence of an improvement over recent years in the representativeness of the trustee population.
“But there is further to go, with the potential to bring even more talent and more diverse perspectives to the fore by supporting more young people and individuals from underrepresented backgrounds to take up trustee roles.
“By encouraging a more diverse range of people to become trustees, we can strengthen boards and better support communities.”