BACKGROUND: Nonsuicidal self-injury (NSSI) has garnered growing attention in recent years, and cybervictimization (CV) has been identified as a risk factor for NSSI among adolescents. However, little is known about this association's longitudinal mediating and moderating mechanisms. Guided by the experiential avoidance model, the present study used a short longitudinal design to examine the mediating role of depressive symptoms and the moderating role of emotional reactivity between CV and NSSI. METHODS: A total of 577 Chinese middle school students (M  = 14.38, SD = 0.67) completed the measures of CV, NSSI, depressive symptoms, and emotional reactivity. They provided data in two waves (T1 and T2, 6 months apart). RESULTS: The results found a longitudinal association between CV and NSSI as well as the mediating role of depressive symptoms. Moreover, emotional reactivity amplified the relationship between CV and NSSI via depressive symptoms; specifically, the relationship between depressive symptoms and NSSI was only significant for adolescents with high emotional reactivity. CONCLUSION: The current study has found that emotional reactivity moderated the indirect effect of depressive symptoms on the relationship between CV and NSSI. These findings have implications for the identification and intervention of NSSI in early adolescents.