The benchmark Korea Composite Stock Price Index lost 2.82 points, or 0.13 percent, to 2,115.78 in the first 15 minutes of trading.
The local shares closed slightly lower Thursday, one day after US President Donald Trump signed the law on support for protesters in Hong Kong, possibly creating a last-minute hurdle in US-China trade negotiations aimed at ending their prolonged trade dispute.
Hit by the lengthy trade negotiations between the world's two largest economies, South Korea's exports have dropped for 11 consecutive months in October. The US and China are also the largest importers of South Korean goods.
The country's export-dependent economy is widely expected to grow at the slowest pace in a decade.
The US stock market temporarily avoided the latest ordeal as it closed for the Thanksgiving holiday, but most European stock markets closed lower Thursday on fears of a possible delay in a US-China trade deal.
Most large caps were in negative terrain in Seoul.
Market kingpin Samsung Electronics shed 0.58 percent, with No. 2 chipmaker SK hynix losing 0.85 percent.
Top automaker Hyundai Motor lost 0.40 percent, while its smaller affiliate Kia Motors slipped 0.45 percent.
The local currency was trading at 1,179.05 won against the US dollar, down 0.05 won from the previous session's close. (Yonhap)