This study examined the mediating effect of perceived stress on the relationship between school violence victimization and non-suicidal self-injury (NSSI). Using data from the 2021 Survey on Mental Health of Adolescents by the Korea Youth Policy Institute, the analysis found that school violence victimization was positively associated with NSSI and that higher levels of victimization were linked to greater perceived stress. Perceived stress, in turn, significantly increased the likelihood of engaging in NSSI. Mediation analysis indicated that perceived stress partially mediated the relationship between school violence victimization and NSSI, suggesting that heightened stress caused by victimization may lead to self-injurious behavior. These findings highlight the need for counseling interventions focusing on stress management and emotion regulation, as well as the importance of school-based systems enabling teachers and counselors to detect and address students’ psychological stress at an early stage.