The institution revealed that its services can now be accessed from iPhones, Palm devices and BlackBerrys.
It comes after Nielsen found that smartphones are increasing in popularity, with a study relating to the first quarter of the year showing nearly a quarter of phones purchased in the previous six months fell into the category.
And with market penetration having reached 16 per cent in the US, Citibank's Peter Knitzer explained that the aim is to make banking "as easy as possible" for consumers.
"With Citi Mobile now available for all smartphones, even more of our customers have access to fast, highly secure day-to-day banking whenever they need it," he said.
Last week, Citibank parent company Citigroup announced the opening of a new facility in Singapore, as it consolidated its operation and technology sites.