Although cyber victimization has been suggested as a significant risk factor for the development of adolescents' depression, the underlying psychopathological process that mediates this relationship needs further exploration. Based on the psychological inflexibility model, this study aimed to examine cognitive fusion and experiential avoidance as serial mediators in the relation between cyber victimization and depression. A total of 556 Chinese adolescents completed a set of online self-report questionnaires measuring cyber victimization, cognitive fusion, experiential avoidance, and depression. A bias-corrected bootstrap approach was used to test the serial mediation model. The results showed that cyber victimization predicted adolescents' depression not only directly but also indirectly through three paths: the mediating role of (1) cognitive fusion and (2) experiential avoidance, and (3) the serial mediating role of cognitive fusion and experiential avoidance. These findings provide insight into the interventions for depression in adolescent cyber victims.