Perceived social support is an important predictor of school mental health outcomes of students. However, more research is needed on the indirect effects in this association. The present study aimed to investigate the direct and indirect effects (via mental toughness) of parent-classmate-teacher support on early adolescents' school mental health. A total of 359 early adolescents (M[subscript age] = 12.77, SD = 0.91) from grades 6 to 8 participated in the research. The child and adolescent support scale, mental toughness scale for adolescents, and psychological wellbeing and distress screener were used as measuring instruments. The results suggest the importance of perceived social support from parents and classmates for school well-being, as well as the importance of mediating role of mental toughness. The present results extend our insight into the mechanism underlying the links between perceived social support and school mental health outcomes. Implications and limitations are discussed, and suggestions for future research are provided.