The available research findings suggest that non-suicidal self-injury (NSSI) constitutes an important public health issue, with identified risk factors for NSSI having been found to include exposure to adverse childhood experiences (ACEs) and comorbidity with various mental disorders. However, the available findings have, for the most part, been based on the experiences of individuals living in predominantly high-income countries located in the Global North, and it is not clear whether these findings can be confidently generalised to individuals living in low-resourced countries. As such, this cross-sectional study assessed risk factors for NSSI in a non-clinical sample of 636 South African adolescents (12–18 years old), with the data being analysed using a multi-mediation analysis. ACEs were assessed using a revised version of the ACEs Questionnaire, and NSSI was assessed using items adapted from the Self-Harm subscale of the Risk-Taking and Self-Harm Inventory for Adolescents, with emotion dysregulation, depression, and PTSD being considered as possible mediators. High prevalence rates for NSSI and exposure to five or more ACEs were reported by the participants, with the mediation analysis indicating that significant direct effects of adverse childhood experiences on NSSI were partially mediated by emotion dysregulation. These findings are discussed with respect to their implications for primary, secondary, and tertiary prevention.