The daily trading volume of local stocks came to some 8.6 trillion won ($7.1 billion) last month, according to the Korea Exchange (KRX), the operator of the Seoul bourse.
The reading marks a drop of 4 percent from the same month last year and also a 3.4 percent decline from the month before.
Such a drop also comes despite a 0.05 percentage-point reduction in the transaction tax to 0.25 percent in May, which marked the first tax reduction in 23 years.
The drop in the daily trading volume apparently came as market investors took to the sidelines amid the intensifying trade conflict between the world's two largest economies, which also delivered a hard blow to major companies here.
The row, which, after a brief pause in June, was reignited after the countries' negotiations failed to produce any visible outcome.
As the world's two largest importers of South Korean products sparred, Seoul's outbound shipments dipped for the eighth consecutive month in July, which in turn resulted in the worst performances in years for many businesses in the export-dependent country.
Investor sentiments further worsened when Japan implemented tougher export restrictions early last month on three key materials used in the production of semiconductors and display panels, both key export items of South Korea.
In July, Seoul's benchmark Korea Composite Stock Price Index (KOSPI) backtracked 5 percent from a month earlier, with the tech-heavy KOSDAQ plunging 8.7 percent.
Of the 100 top market caps, 80 saw their stock prices dwindle from a month earlier in July, according to the KRX.
The outstanding loans for stock purchases extended by securities firms also dropped to some 9.4 trillion won as of end-July, down from 10.4 trillion won a month earlier. (Yonhap)