BackgroundSelf-harm seriously endangers adolescents' physical and mental health. However, the longitudinal mechanism of self-harm is not yet clear. ObjectiveThis study explored the inconsistent relationships between two types of emotional maltreatment and self-harm across three waves, regarding depression as a potential mediator and gender as a moderator of these associations. Participants and settingA sample of 588 Chinese adolescents (Mage at T1 = 12.79 years) in a middle school completed the assessment of demographic information, emotional maltreatment, depression and self-harm within one year. MethodsPath analysis models were created to estimate the relationship of emotional maltreatment with self-harm and the mediating effect of depression. A multi-group analysis was applied to investigate the moderating effect of gender. ResultsThere existed positive associations between emotional abuse at T1 and self-harm at T2 and T3 (β = 0.12, SE = 0.05, p = 0.006; β = 0.09, SE = 0.05, p = 0.054), and the mediating effect of emotional abuse at T1 on self-harm at T3 via depression at T2 was significant (Indirect effect = 0.05, SE = 0.02, 95 % CI [0.02, 0.08]). Multi-group analysis of gender revealed no significant differences in the cross-lagged pathways, but there were stronger links for girls than boys among self-harm at T1, T2, and T3 (p < 0.001). ConclusionsEmotional abuse but not emotional neglect could significantly predict self-harm. Furthermore, depression played a mediating role in the longitudinal relationship between emotional abuse and self-harm. Girls who had high levels of self-harm at a previous time point were more inclined than boys to harm themselves at a subsequent time point. These findings provide a different perspective to develop effective prevention and intervention measures.