The data released by the world's seventh-largest exporter also eases concerns the global economy could slip back into a slump on the stubbornly high U.S. unemployment and the fallout from Europe's debt crisis.
Analysts said the figures along with Friday's data showing a pick-up in December inflation would easily offset any economic fallout from the heightened tension with North Korea and persuade the central bank to keep raising interest rates.
"Strong exports will certainly prevent the (South Korean) economy from slowing rapidly while inflation is gathering pace. So I don't see any problem with the view of more interest rate increases ahead," said Park Sang-hyun, chief economist at HI Investment & Securities.
"I think the Bank of Korea will raise the rate in February at the earliest."
Exports grew 23.1 percent to a record $44.34 billion in December from a year before, while imports increased 23.3 percent to $40.60 billion , producing a trade surplus of $3.74 billion , the Ministry of Knowledge Economy data showed.
All figures are provisional.
The median forecast from a Reuters survey of analysts were for exports to rise 19.1 percent in December from a year earlier and imports by 20.4 percent. Forecasts for export growth ranged from 16.1 percent to 23.6 percent.
Sales rose strongly to almost all regions, except for the European Union markets hit by a fiscal crisis, and oil products, steel products and cars were the hottest selling items, the ministry data showed.
The average export value per working day -- a useful measure of monthly changes as the country does not provide seasonally adjusted figures -- rose to $1.81 billion in December from a revised $1.72 billion in November, Reuters calculation shows. Government data showed on Friday consumer inflation rose to an annual rate of 3.5 percent in December from November, defying the median forecast for slowdown in a Reuters survey.
Solid economic growth and signs of rising inflation prompted the Bank of Korea, the central bank, to raise interest rates twice in 2010.
It last raised the benchmark interest rate in November by 25 basis points to 2.50 percent and next reviews the rate on Jan. 13.
South Korea was among the top performing economies in the Organisation for Economic Co-operation and Development group last year and is tipped to be one of the top three this year.