Business sentiment for August fell to the lowest level since just after the 2008 global financial crisis. The index, which measures future outlook based on a survey of the nation's top 600 businesses by the Federation of Korean Industries, stands at 82.7 points.
The lowest BSI was 76.1 points in March 2009, when the impact of the global financial crisis was being felt around the world. A reading below 100 means pessimists outnumber optimists.
"It appears that businesses have a gloomy outlook of the economy due to concerns that the eurozone crisis could spread to Germany and other key European countries or that China's economy will falter," an FKI spokesman said.