Recent decades have witnessed rapid growth of K-12 transnational education programs, but little is known about how human/nonhuman assemblages impact K-12 transnational literacy curricula and how sociomaterial assemblages affect (de)colonizing literacy practices. This study of English and Mandarin literacy curricula at a Canadian transnational education program in postcolonial Hong Kong was informed by posthumanism and theories on decolonizing curriculum. The study combined ethnographic data collection tools (curriculum documents, interviews, classroom observations) and a diffractive methodology of reading, thinking, and writing with multiple data sources and theories to explore how sociomaterial relations between humans and nonhumans shaped the (de)colonization of literacy curricula. Findings show a generative sociomaterial assemblage in the transnational education program that enabled encounters of local-global curricula, local-global languages, and academic-multimedia literacies. New forms of imperialism and colonialism also joined the assemblage and normalized binaries of L1/L2, local/global, and academic/multimedia literacies, thus constraining students' meaning making across languages, places, and semiotic resources. The article proposes literacy curriculum and pedagogies that could foster students' ethical relationship building with humans and nonhumans in globalized schooling contexts.