Net profit for the July-September period stood at 657 billion won ($620 million), compared to 903 billion won in the same quarter last year.
Operating profit was also down 18.6 percent at 567 billion won.
A no-discount policy based on the popularity of Kia's new models abroad and efficient marketing expenditure prevented a further drop in earnings, the company said.
Car sales rose 13 percent over the same quarter last year, but Kia said the increase was overshadowed of a strong won and weak yen that gave rival Japanese carmakers an advantage.
Overseas sales account for more than 80 percent of Kia's business. Kia is a subsidiary of Hyundai Motor, which reported Thursday a 28.3 percent plunge in net profit for the same quarter.