Consumers often rely on observable cues that hint at the hidden quality of a product. The aim of this study was to investigate brain activities associated with the country-of-origin (COO) effect and consumer evaluation of a product design. Electroencephalogram recordings were used to observe event-related brain potentials associated with the COO effect and design evaluation. We found that the frontocentral N90 and parieto-occipital P220 amplitudes are involved in forming preference to design, whereas the COO effect is processed in the centroparietal P500 amplitude. We also found a significant interaction effect between COO and design preference with regard to reaction times. Specifically, participants tended to spend more time making a preference decision when they did not like the product design made in a country with a favorable COO. These results imply that the two cognitive processes, evaluation of COO and formation of design preference, are activated independently at an early stage. It also suggests that these two processes interact with each other toward the end of the decision phase. Together, the results of this study provide neuropsychological evidence supporting a significant role of COO in the formation of design preference. Future studies are required to further delve into other neurophysiological activities associated with the COO effect.