This paper argues that transnational new media space is an important developmental context for migrant youth who have multiple social networks across geographical and cultural locations. Informed by the ecological model of development and literacy studies, this paper examines Korean migrant adolescents’ sense of self and belonging in relation to the three intertwined identity categories – nationality, race, and ethnicity; and the role of new media in youth’s identity negotiation and representation. Using an ethnographic case study design, this paper analyzes adolescents’ identity work reflected in their verbal interviews and multimodal new media literacy practices. Findings suggest that despite the complexity of youths’ identity as seen in their shifting meaning of being Korean across national, ethno-cultural, and racial contexts, youths actively reconstructed and shared a fuller range of their identity constructs drawing on the resources and linguistic tools in transnational new media. Keywords: migrant youth, replenished ethnicity, transnationalism, identity work, new media