The Korea Development Institute says the local economy has remained "stagnant" for seven consecutive months.
In its monthly report released today, the think-tank said growth is being weighed by sluggish exports and investments, despite an uptick in consumption.
Korea's exports in September tumbled nearly 12 percent on-year amid a slowing global economy.
Production of electronic components and cars also fell around 17 percent and 12 percent, respectively.
Although consumption rose, it may have been a one-off gain due to an early thanksgiving holiday this year that boosted retail sales in August.
The rise was also attributed to increasing tourism to Jeju Island, with many travelers boycotting trips to Japan amid the Seoul-Tokyo trade dispute.