The COVID-19 pandemic has not only been a health crisis but also a turning point that deepened debates on justice and inequality at the global level. One of the most critical phases of the pandemic-the development and distribution of vaccines-brought the concept of “vaccine nationalism” to the forefront. Vaccine nationalism is defined as states prioritizing limited vaccine supplies for their own citizens, engaging in large-scale stockpiling, and relegating international solidarity to a secondary position (Fidler, 2021). This situation particularly restricted access to vaccines for low- and middle-income countries and made inequalities in global health more visible. Although global mechanisms such as the World Health Organization (WHO) and COVAX undertook significant initiatives with the aim of ensuring equitable vaccine distribution, the economic and political priorities of powerful states often limited the effectiveness of these mechanisms (Eccleston-Turner & Upton, 2021). Thus, the pandemic emerged as an arena where the preservation of the “global common good” and the pursuit of national interests clashed within international relations. This article examines vaccine nationalism in the context of global inequality and discusses its consequences in terms of both international cooperation and health diplomacy. While highlighting the unequal effects of the pandemic, the study also explores how the concept of justice in global health has been redefined in the international system. The findings demonstrate that vaccine nationalism is not merely a short-term crisis management preference but a phenomenon that reproduces permanent injustices within the global order.