Science has recently emerged as a key concept in understanding the process of nation-state building. The relationship between science and nationalism may be explored from various angles, but most research examines the relation only in its ideological aspect, without paying much attention to how deeply nationalism has been intertwined with scientists' everyday work—including their research agendas and methodologies. This essay examines the practices of Korean biologists during the Japanese colonial period (1910–45), focusing on how the members of an emerging occupational category connected their research with cultural nationalism. Depending on their respective career patterns, they had different ideas about research objects, methods, and the very nature of science. A central figure in this essay is the Korean taxonomist Seok Ju-myeong 石宙明 (1908–50), who found in nationalism a helpful resource to guide his taxonomical research on butterflies. He maintained that he was doing “Korean biology” since the unique characteristics of indigenous fauna and flora played an essential role in guiding his work. Seok is a fine case of the codevelopment of nationalism and scientific research.