The figure, which is based on "raw" data and does not take into account seniority, title or location, marks a slight reduction on the previous year, when its gender pay gap stood at 29%.
The pay gap for U.S. minorities was 6%, a percentage point less than the previous year.
To be sure, when adjusted to compare like-for-like employees, the bank said its female staff were paid 99% of what their male counterparts were paid. But it noted that it had further to go; writing in a blog post that it had made "appropriate pay adjustments" this year to balance the salaries of comparable roles.
The announcement marks the latest step by the U.S.'s third-largest bank to move the needle on pay equality. When a law forcing corporations to disclose their unadjusted pay gap figures went into effect in the U.K. in 2018, Citigroup became the first bank to voluntarily release its data on a global scale.
"Transparency breeds accountability and we took that important first step last year in disclosing our pay equity results," Citigroup's global head of human resources, Sara Wechter, said to Reuters in a statement.
But it still has a long way to go, and reducing the global gap will mean promoting more women to the top levels of management.
"Continuing to reduce our raw pay gap requires that we make progress on our representation goals ... which we are committed to doing," Wechter wrote in the blog post.
The bank is now aiming for female employees to hold 40% of assistant vice president to managing director level roles by 2021, with 8% of such roles in the U.S. to be held by black employees.
It has already made steps in this regard. Of the total 45 managing directors the bank promoted in Asia-Pacific in December, 31% were women — up from 21% in 2018, according to a report in The Business Times. Yet Wechter was keen to point out that its overall figures were likely to fluctuate over time.
"Our work to address both measures is continuous and the pace of change is likely to vary from year to year," wrote Wechter.
"As people come in and out of the firm, as our colleagues are promoted and as market dynamics change, these reviews are important measures of how we're doing on our commitment to pay colleagues equitably for their work and of the progress we're making to increase diversity at more senior levels at Citi."
Like this story? Subscribe to CNBC Make It on YouTube!