The country's biggest carmaker by sales sold 336,625 vehicles in August, down from 358,252 units a year earlier, the company said in a statement.
Declining demand from China triggered by the diplomatic row between Seoul and Beijing over the deployment of the Terminal High Altitude Area Defense system continued to affect monthly sales figures, the carmaker said.
Domestic sales rose 30 percent on-year to 54,560 cars last month from 42,112 a year earlier. But overseas sales contracted 11 percent to 282,065 from 316,140 during the same period, it said.
In the January-July period, Hyundai saw its sales plunge 41 percent to 351,292 units in China, the world's biggest automobile market, from 592,785 a year earlier.
China has halted all tour packages to South Korea and penalized other manufactured goods as part of its retaliation against the stationing of the THAAD system. Seoul and Washington maintain THAAD is purely aimed at countering missile threats from North Korea. But Beijing has opposed the system, arguing it could be used against it.
From January to August, Hyundai sold 2.87 million autos, down 7.2 percent from 3.09 million during the year-ago period, it said. (Yonhap)