Through an in-depth case study of the instant messaging practices of an adolescent girl who had migrated to the United States from China, this qualitative investigation examines the development of multiliteracies in the context of transnational migration and new media of communication. Data consisted of screen recordings of the youth's digital practices, interviews, and observations. Data analyses included qualitative coding procedures and orthographic analysis of the use of multiple dialects and languages in the youth's instant messaging exchanges. These exchanges illustrate the process of social and semiotic design through which the youth developed simultaneous affiliations with her local Chinese immigrant community, a translocal network of Asian-American youth, and transnational relationships with her peers in China. The construction of transnational networks represents the desire of the youth to develop the literate repertoire that would enable her to thrive in multiple linguistic communities across countries and mobilize resources within these communities. This study contributes to new conceptual directions for understanding translocal forms of linguistic diversity mediated by digital technologies and an expanded view of the literate repertoire and cultural resources of migrant youth. As such, this study's contributions are not limited to the domain of digital literacies but extend to issues of linguistic diversity and adolescent literacy development in contexts of migration. (Contains 1 table and 1 note.)