The decision to leave the rate untouched had been widely expected as the Bank of Korea pauses to judge the impact of last month's decision.
The August cut was the first since May 2013, and came after the finance ministry in July unveiled a $40 billion stimulus package and revised its 2014 economic growth forecast down from 4.1 percent to 3.7.
Some economists say the central bank may ease its monetary policy once again before the end of this year if the economy does not pick up strongly.
Gross domestic product rose a seasonally adjusted 0.6 percent in the April-June period from the previous quarter.
It was the slowest growth since the first quarter of 2013, and missed market expectations of around 0.7 percent.
Year-on-year, Asia's fourth largest economy expanded 3.6 percent in the second quarter, down from the previous quarter's 3.9 percent.