This dissertation is a study about Korean immigrant students' identities, including academic identities related to science learning and identities along various social dimensions. I explore how Korean immigrant students participate in science classrooms and how they enact and negotiate their identities in their classroom discursive participation. My dissertation is motivated by the increasing attention in educational research to the intersectionality between science learning and various dimensions of identities (e.g., gender, race, ethnicity, social networks) and a dearth of such research addressing Asian immigrant students. Asian immigrant students are stereotyped as quiet and successful learners, particularly in science and mathematics classes, and their success is often explained by cultural differences. I confront this static and oversimplified notion of cultural differences and Asians' academic success and examine the intersectionality between science learning and identities of Asian immigrant students, with the specific case of Korean immigrants. Drawing upon cultural historical and sociolinguistic perspectives of identity, I propose a theoretical framework that underscores multiple levels of contexts (macro level, meso level, personal, and micro level contexts) in understanding and analyzing students' identities. Based on a year-long ethnographic study in two high school Advanced Placement Biology classes in a public high school, I present the meso level contexts of the focal school and biology classes, and in-depth analyses of three focal students. The findings illustrate: (1) how meso level contexts play a critical role in these students' identities and science classroom participation, (2) how the meso level contexts are reinterpreted and have different meanings to different students depending on their personal contexts, and (3) how students negotiated their positions to achieve certain identity goals. I discuss the implications of the findings for the science education of racially, ethnically, and linguistically diverse students, particularly given the increasing number of immigrant students in U.S. classrooms, and for the education of Asian immigrant students.