The consumer price index rose 1.1 percent from a year ago, following a 1.4-percent increase in August, the state-run Statistics Korea said.
It was the slowest pace since February when it rose 1.0 percent.
The core consumer index, which excludes volatile energy and food prices, rose 1.9 percent compared to a 2.4 percent increase in August.
The latest figure remained far below the central Bank of Korea's annual target range of 2.5 to 3.5 percent.
The central bank expects inflation in Asia's fourth-largest economy to accelerate to 1.9 percent in 2014 following a 1.3 percent increase in 2013 -- the slowest for 14 years.