The Bank of Korea said the 2012 growth rate was unchanged from its January projection.
The bank also revised the growth rate for 2011 to 3.7 percent from its estimate of 3.6 percent. Growth in 2013 was estimated at 2.8 percent.
South Korean economy is Asia's fourth largest, after those of China, Japan and India.
South Korean exports, which account for about 50 percent of the economy, grew 4.2 percent in 2012, down from 9.1 percent gain in 2011, the bank said.
"Lackluster consumer spending and facility investment caused the economic growth to slow down last year," Jung Young-taek, the director of the BOK's national accounts division said in a Yonhap report.
It isn't clear if the bank would cut its key interest rate next month from the current 2.75 percent, which has remained unchanged for five months.
Yonhap said the government is expected to unveil a package of stimulus measures that may include $90 million in extra budget plans.