Bullying victimization is a serious issue that causes adverse effects for children and adolescents. Within the school context, few studies have investigated the underlying mechanisms between such victimization and belonging. Using a representative sample of Chinese students from the Program for International Student Assessment 2018 (PISA 2018), this study investigates the relationship between bullying victimization and school belonging, the mediating roles of student competition and cooperation, and the moderating role of gender. Results show that bullying victimization has a significant and negative predictive effect on school belonging. Student competition and cooperation partially mediate this relationship. The direct predictive effect of bullying victimization on school belonging is moderated by gender, with a stronger effect for females than for males. The findings provide new perspectives for intervention programs to improve school belonging of Chinese students.