Background: Non-suicidal self-injury (NSSI) is a serious and alarming phenomenon during adolescence. There is a need for understanding the intrapersonal variables that might contribute to the maintenance of these self-injurious behaviors. Objective: This study aims to concurrently compare intrapersonal variables between adolescents with and without a lifetime history of NSSI, and to longitudinally test whether NSSI over lifetime history predicts 6-months NSSI through self-criticism and depressive symptoms among Portuguese adolescents with a self-reported history of NSSI. Methods: Adolescents (N = 418, 12-19 years-old) from middle and secondary schools completed self-report questionnaires to assess self-criticism (particularly, the most severe form: hated self), depressive symptoms, and the frequency of NSSI in two points in time over the 6-months interval. Results: Adolescents who reported a lifetime history of NSSI tend to experience greater harsh and persecutory criticism towards themselves and elevated depressive symptoms than adolescents without a history of NSSI. Results from path analysis showed that lifetime NSSI predicts subsequent NSSI, and this association is mediated by self-hatred and depressive symptoms among adolescents with lifetime NSSI. Conclusions: Findings suggest that NSSI is maintained through a sense of self-focused on hatred and disgust feelings and depressive symptoms.