Though lower than the previous month, the Bank of Korea said the July figure represented the 18th straight month of surplus, credited to export growth.
The current account is the broadest measure of a country's trade with other nations. A surplus is reported when receipts from exports and financial transfers exceed money spent on imports of goods and services and money transfers.
South Korea is Asia's fourth-largest economy, after China, Japan and India.
The BOK said the smaller surplus in July was mainly because spending on overseas travel rose during the summer vacation season.
South Korea's current account surplus totaled $36.55 billion in the first seven months of this year.
Yonhap News Agency reported the central bank sharply increased its estimate of current account surplus for all of 2013 to $53 billion from the previous estimate of $33 billion. If achieved, the full-year surplus would be a record high, topping last year's $43.14 billion, the report said.
The impressive numbers come at a time when some emerging markets such as India and Indonesia are facing foreign capital outflows, which have caused a sharp depreciation of their currencies. The outflows have been sparked by concerns the U.S. Federal Reserve may soon begin to taper off its monetary stimulus, which would choke off the availability of cheap money for investing in emerging markets.
The current account surplus also has helped boost South Korea's foreign exchange reserves, which help cushion the impact of external funding risks.