The International Baccalaureate (IB), established in the 1960s, is recognized worldwide for its high-quality and intercultural educational programs at primary and secondary school level. These programs are particularly popular in contemporary Asian societies, where they serve as a competitive option for parents looking for international standards in education. This chapter focuses on IB schools in three of the Four Asian Tigers—Taiwan, Hong Kong, and Singapore—areas known for their developed, export-oriented economies and multicultural, postcolonial histories. Using an analytical framework based on the three pillars of institutional legitimacy—regulative, normative, and cultural-cognitive aspects, as discussed by researchers like Bunnell, Fertig, and James (Educ Rev 69(3):303–317, 2017) and Scott (Institutions and organizations: ideas, interests, and identities. Sage, Thousand Oaks, 2014)—this study analyzes how IB schools have integrated into local education systems while maintaining their distinct international identities. From 2020 to 2023, the research included semi-structured and in-depth interviews with 43 participants across 15 IB schools in the three regions. These interviews revealed insights into implementing and operating IB programs within these distinct cultural and educational environments. The chapter further explores the role of institutional legitimacy in contextualizing the IB within local settings with Scott’s (Institutions and organizations: ideas, interests, and identities. Sage, Thousand Oaks, 2014) framework. The findings show how these schools have developed strategies to remain competitive by aligning their curricula with local educational values and demands, thus attracting families interested in global citizenship and maintaining relevance in a globalized educational landscape.