The purpose of this study was to theorize instructional language choice process of Chinese Korean teachers through based on grounded theory. Interviews and qualitative data were collected from five Chinese Korean teachers, and the data were theoretically analyzed through continuous comparative analysis. I first explored 79 concepts, 33 subcategories, and 17 categories using open coding. Using the open coding results, I categorized the process of using L1 according to the paradigm model. The analysis showed that the central phenomenon is the difficulty in determining an instruction language between the L2 and L1. To solve this problem, Chinese Korean language teachers expanded the use of L1. The first process in the use of L1 is the recognition stage for their unique role as non-native teachers, followed by the stage of sharing roles with native Korean teachers and, finally, the stage of successful role-playing. The above results suggest that L1 is used as a tool for self-awareness of Chinese Korean language teachers and their roles and for performing the roles. Furthermore, it is significant that the use of Chinese Korean teachers’ L1 is related to teacher identity beyond the cognitive and affective factors.