<p>Previous theory and research indicate an intricate connection between bullying victimization, self-esteem, and prosocial behavior. However, longitudinal evidence remains limited regarding the within-person reciprocal association between bullying victimization and prosocial behavior, whether their association operates indirectly through self-esteem, and whether these patterns differ between boys and girls. The current three-year longitudinal study, with a one-year interval, applied the RI-CLPM to explore the reciprocal relationship between bullying victimization and prosocial behavior, as well as the mediating role of self-esteem, separately for boys and girls. Data from 2,530 Chinese adolescents (51.40% boys; age = 13.29 ± 0.51 at T1) were analyzed. Results revealed a within-person reciprocal relationship between bullying victimization and prosocial behavior among boys only. By contrast, girls showed no direct within-person reciprocal effects. Instead, the longitudinal reciprocal relationship was mediated by girls’ self-esteem. Specifically, girls’ self-esteem at T2 mediated both the path from bullying victimization at T1 to prosocial behavior at T3 and the reverse path from prosocial behavior at T1 to bullying victimization at T3. These findings emphasize the need for gender-specific interventions, with a focus on promoting prosocial behavior for boys and enhancing self-esteem for girls to reduce the negative consequences of bullying victimization.</p>