The world's fifth-largest crude oil buyer imported a total 81.71 million barrels of crude oil in January, up 2.8 percent from a year earlier, the data showed.
Preliminary data from the economy ministry showed earlier this month that South Korea's crude oil imports in January rose 0.9 percent from a year earlier to 80.1 million barrels.
South Korea is one of Iran's biggest oil customers, but imports have fallen as European Union sanctions made it tough to ship, insure and pay for the oil. The West has imposed sanctions on Iran as it suspects Tehran wants to develop nuclear weapons, a claim Iran denies.