This research intended to examine the effect of mindset, democratic parenting, democratic teaching, and school environment on global citizenship among 2,226 ninth-grade students and 80 social studies teachers from 80 classrooms in public schools. The research instruments included a student questionnaire to measure global citizenship, democratic parenting, fixed and growth mindset, and a teacher questionnaire to measure democratic teaching and school environment and to analyze the data based on multilevel structural equation modeling. The significant findings revealed that democratic parenting and school environment positively affected global citizenship, whereas democratic teaching had a negative effect on global citizenship. In addition, the outstanding students with a growth mindset tend to lead to a positive effect and act as a mediating role through global citizenship than those with outstanding fixed mindset clearly. All factors in the model collaboratively explained the variance of global citizenship accounted for 62.8% and 47.5% at student and classroom levels, respectively. Finally, the discussions and suggestions section suggested the recommendations according to the findings of the research.