Informed by positioning theory as well as a nexus of multimembership, the year-long case study examined how a 7-year-old Korean American bilingual child, Meeso, constructed her ethnic identity across different educational contexts. Data were collected through observations of Meeso's interactions with her monolingual and bilingual peers and teachers. Discourse analysis revealed that Meeso constructed fluid ethnic identity positionings depending upon how she desired to position herself and to be positioned by others. We also identified that the social context, language proficiency, and peer dynamics were related to the process. Based on the findings, we discuss the roles of context, language, and peer interaction for bilingual students' ethnic identity development.