The group's 2017 Financial Services Gender-Equality Index (BFGEI) found an average of 24.2 per cent female representation on the 52 boards it surveyed, which include Barclays, American Express and Royal Bank of Scotland.
"We are encouraged by the significant expansion of this year's index, and by the leadership each of our member firms has demonstrated," said Peter T Grauer, chairman of Bloomberg and founding chairman of the US 30 per cent Club.
"Their commitments to building diverse and inclusive work environments are setting new standards around the globe and raising awareness around the challenges all of our organisations face," he added.
Of the member firms, 73 per cent require a gender-diverse slate of candidates for management roles, 83 per cent offer or sponsor financial education programmes for women in their communities, 75 per cent provide return-to-work programmes and nine track repayment rates by gender.
"Companies are increasingly focused on managing operational risks, including the attraction and retention of employees," said Angela Sun, head of strategy and corporate development at Bloomberg.
"The BFGEI brings greater transparency to the practices and policies crucial to managing those risks and attracting investor capital," she added.
The 2017 BFGEI recognises firms headquartered in 17 countries, expanding to Australia, Brazil, India, Japan, Hong Kong, Malaysia, Mexico, Sweden and Turkey.