The country's current account surplus reached $7.48 billion in September, compared with a surplus of $11.01 billion a year earlier, according to the preliminary data from the Bank of Korea.
The figure represents a surplus for five months in a row. The current account is the biggest measure of cross-border trade.
The September tally, however, marks the highest since October last year when the comparable figure was $9.35 billion, the data showed.
Park Dong-jun, head of the balance payment team at the BOK, said slowing exports were to blame for the narrowed current account surplus.
The goods account surplus narrowed to $8.84 billion from $13.01 billion over the cited period, due to a large cut in exports. Exports fell 10.3 percent on-year to $46.01 billion September, with imports declining 3 percent to $37.17 billion.
The BOK said the travel balance-related deficit narrowed to $780 million in September from a deficit of $1.15 billion a year earlier.
In the first nine months of the year, the country logged an accumulated current account surplus of $41.46 billion.
Park Yang-su, director general of the BOK's Economics Statistics Department, said the travel balance-related deficit narrowed as the number of South Korean travelers to Japan dropped sharply amid tensions over Japan's export curbs against South Korea.
The number of South Korean travelers to Japan fell 58.1 percent in September from a year earlier.
The number of Chinese and Japanese tourists to South Korea, meanwhile, jumped 24.6 percent and 1.3 percent, respectively, in September from a year earlier, the BOK said.
The primary income account surplus came to $1.4 billion in September from a surplus of $970 million a year earlier. (Yonhap)