School bullying is prevalent among senior-grade pupils, with negative impacts on pupils' physical health and psychosocial adjustment. However, few studies have explored the relationship between the senior-grade pupils experiencing teacher unfairness and their suffering from school bullying. This study aims to investigate the longitudinal associations between perceived teacher unfairness and school bullying victimization, as well as the mediating role of the sense of school belonging therein. The data were collected from 822 pupils ranging from Grade Four to Five (430 boys and 392 girls, M[subscript age] = 10.8, SD[subscript age] = 0.69 at Time 1) over three semesters. The results indicated that (1) perceived teacher unfairness (Time 1) exerted a significantly negative prediction effect on subsequent school bullying victimization (Time 3); (2) the sense of school belonging (Time 2) played a key mediating role in the association between perceived teacher unfairness (Time 1) and school bullying victimization (Time 3); (3) compared to girls, the predictive effect of the sense of school belonging (Time 2) on school bullying victimization (Time 3) was stronger for boys. The results demonstrated the importance of ensuring teacher fairness and cultivating pupils' sense of belonging to the school as a method of preventing school bullying, and also explained the gender differences between boys and girls; thus, the study provided a theoretical and practical basis for preventing bullying in schools.