The purpose of this article is to examine the level of social capital and global citizenship in Taiwan. In this study, we argue that high social capital and political self-efficacy promote the outcomes of global citizenship. We review the development of global citizenship education policy and its association with social capital and political self-efficacy. Based on the nationwide survey dataset collected from Taiwanese universitiy students, we carefully examine the relations between social capital, political self-efficacy, and global citizenship. We adopt a multiple mediation analysis with a bootstrapped method to validate our conceptual research model. The results show that there are significant positive relationships between the nine observed variables (i.e., social trust, social proactivity, political self-efficacy and six global citizenship outcomes). In addition, our findings of mediation analysis reveal that social capital, indicated by social trust and social proactivity, indirectly affects the five outcomes of global citizenship through political self-efficacy, except for the outcome of global environmental sustainability. In light of the empirical results, this article also discusses the implications of global citizenship education policy and the formation of sustainable global citizenship.