This multi-sited ethnographic case study documents a second-generation Korean immigrant child who engages in regular border-crossing experiences between the U.S. and South Korea, his father's country of origin. Pairing a transnationalism framework with the concept of funds of knowledge, this study examined how border-crossing experiences and transnational engagement shapes the focal immigrant child's funds of knowledge and what he does with his transnational funds of knowledge. With the illustrative examples gathered across cultural boundaries and geographic borders, I discuss how transnational mobility constructed and expanded the focal child's depth of historical knowledge and the ways he transmits and mobilizes his historical knowledge beyond local-global spaces through transcultural play. This article emphasizes the need to create an educational space that makes immigrant children's agency in learning and transnational resources more visible. Furthermore, it offers new guidelines for documenting the connectivity and flow of young immigrant children's knowledge and experiences in the context of transnational migration.