Nonsuicidal self-injury (NSSI) is a common phenomenon among adolescents and represents an important marker of risk for both mental disorders and suicidal behavior. Despite growing clinical and research interest in NSSI during recent years, our understanding of underlying risk-factors and potential pathomechanisms is still limited. This symposium will present latest research findings on psychological, social and biological mechanisms that may contribute to the development and maintenance of NSSI. Data from clinical research reveal that psychopathological distress and personality pathology (in particular identity disturbances) seem to specifically contribute to NSSI. From a social perspective, the phenomenon of social contagion of NSSI, including the influence of social networks, will be a focus of the symposium. From a neurobiological perspective, new findings of alterations of pain perception and biological reactivity to pain as well as alterations of the neurobiological stress response systems will be presented. In addition to new data on social and biological mechanisms of NSSI, the symposium aims to integrate these findings into a comprehensive understanding of NSSI, and to translate latest research findings into recommendations for prevention and intervention in adolescent NSSI.