AIM: This study investigated the mediating effects of perceived opportunity in adversity and PTSD symptoms in the relationship between relationship loss and non-suicidal self-injury (NSSI) in adolescence. BACKGROUND: Adolescent relationship loss can have lasting negative effects on development and later life, and may particularly increase the risk of NSSI. The consequences of relationship loss vary depending on the individual's perception and psychological responses. However, the mechanisms by which adolescent relationship loss leads to NSSI are not yet clear, and research on the role of perceived opportunity in adversity and PTSD symptoms in this context is limited. METHODS: The convenience sample included 201 college students who had experienced both relationship loss and NSSI during adolescence. Data were collected using four self-report measures (relationship loss, perceived opportunity in adversity, PTSD symptoms, and NSSI) and analyzed using structural equation modeling (SEM). RESULTS: PTSD symptoms partially mediated the relationship between relationship loss and NSSI. In addition, perceived opportunity in adversity and PTSD symptoms sequentially mediated the relationship between relationship loss and NSSI. On the other hand, perceived opportunity in adversity did not mediate the relationship between relationship loss and NSSI. CONCLUSION: Reducing PTSD symptoms may mediate the impact of adolescent relationship loss on NSSI, while the bidirectional nature of perceived opportunity in adversity warrants attention. Counselors and educators should implement strategies to alleviate PTSD symptoms and develop programs that leverage the positive aspects of perceived opportunity in adversity to mitigate negative outcomes.