Government data released Monday showed exports down 18.5 percent from the same month last year at $36.7 billion -- the steepest decline since August 2009.
The report cited a host of factors, such as slowdowns in major economies, including South Korea's biggest trade partner China which accounts for a quarter of the country's exports.
Falling global oil prices also contributed to the dismal figure, hitting petroleum products that are a mainstay export item for Asia's fourth largest economy.
South Korea's exports declined every single month last year, resulting in the slowest annual economic growth since 2012.
Overseas shipments for the entire year were down 8.0 percent -- the first annual contraction for three years.
South Korea's economy expanded by 2.6 percent in 2015, coming in just under the forecast 2.7 percent.