The February rate in Asia's fourth-largest economy was the highest since March 2011, when it was 4.3 percent, Statistics Korea said, Yonhap News reported.
The report said job creation slowed to 447,000 jobs in February year-on-year, compared to 536,000 in January.
"The jobless rate tends to rise in February as soon-to-be graduates start to find work. In addition, as more people applied for government-led job programs and public-sector positions, the figure seems to have increased further," Statistics Korea said.
South Korea's export-dependent economy has continued to improve despite global market uncertainties such as the eurozone debt crisis.
South Korea reported a trade surplus of $2.2 billion in February, attributed to rising overseas demand for its goods. The February figures were even more impressive, considering the country had a trade deficit of $2.03 billion in January.
"More people seem to be resuming job-seeking efforts, emboldened by improving economic conditions," one analyst told Yonhap.
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