The benchmark Korea Composite Stock Price Index (KOSPI) lost 7.15 points, or 0.37 percent, to 1,943.86 in the first 15 minutes of trading.
The drop came despite overnight gains on Wall Street ahead of the Jackson Hole Fed meeting, where US Federal Reserve Chairman Jerome Powell is widely expected to hint at a rate reduction down the road.
The Dow Jones industrial average added 49.51 points, or 0.19 percent, to close at 26,252.24.
Large caps traded mixed, while techs and chemicals were in negative terrain.
Market kingpin Samsung Electronics shed 0.34 percent, while top chemicals firm LG Chem lost 0.31 percent.
Leading pharmaceutical company Celltrion slipped 0.66 percent, while top automaker Hyundai Motor gained 0.81 percent.
The local currency was trading at 1,211.15 won against the US dollar, down 3.75 won from the previous session's close. (Yonhap)