Non-suicidal self-injury (NSSI) includes behaviours such as cutting and burning oneself. Some adolescents who self-injure experience suicidal thoughts and NSSI has been identified as a potential suicide risk factor. We aim to longitudinally investigate factors placing adolescents at risk of engaging in NSSI, and why some experiment briefly with self-injury while others become reliant on these behaviours. We will survey, interview, and conduct focus-groups with Wellington-area adolescents over time to investigate how intrapersonal factors (e.g. mental health, emotional regulation), interpersonal factors (e.g. victimisation, connectedness to peers and whanau), and the socio-cultural environment (e.g. peers, school, kura, and social norms) influence development, maintenance, and cessation of NSSI. Through interviewing adolescents, caregivers, and school counsellors, we will examine barriers to help-seeking experienced by adolescents. Throughout the research, we will develop resources for each of these groups to facilitate help-seeking, including graphic novels targeting adolescents, professional development for counsellors, and information for caregivers.