The purpose of this study was to investigate the school-related factors that influence students' global citizenship. To explore both student-level and school-level factors that influence students' global citizenship, we applied a hierarchical linear model using PISA 2018 data from Korea. The results showed that factors related to teacher's GCED practices and school climate can play an important role in fostering students' global citizenship. Based on these findings, we suggest that a whole-school approach is needed to promote the inclusion of GCED-related topics in various school curricula and to integrate GCED values into the overall school culture to enhance students' global citizenship.