This study examined the product adaptation behavior of Korean export firms (voluntary product adaptation vs. involuntary product adaptation), the resulting degree of product adaptation and export performance, and the internal firm factors that distinguish these product adaptation behaviors. The results showed that voluntary product adaptation exporters exhibited a higher degree of product adaptation than involuntary product adaptation exporters. However, regarding export performance (export intensity, export growth rate, export profit rate), although voluntary product adaptation firms showed better absolute values than involuntary adaptation firms, the differences were not statistically significant. Meanwhile, it was found that the major internal firm factors distinguishing voluntary from involuntary product adaptation exporters included the presence of a dedicated export department, export planning, budget allocation for overseas market research, the existence of a technology development department, the number of export destination countries, top management's commitment to internationalization, the proportion of exports under own brand names, and the quality competitiveness of export products.