Introduction: The purpose of this study was to explore the prevalence of self-harm and the psychosocial factors associated with self-harming behaviours in youth admitted to an in-patient psychiatric unit. Methods: Cross-sectional surveys of standardized measures were administered to youth and a separate survey to their caregivers while the youth were in hospital. Results: The mean age of the 123 youth who participated was 15.74 (SD 1.51) years, and 90 of 121 (74.38%) reported being female. Of the 115 who completed this question, 101 (87.83%) indicated that they thought of injuring themselves and 89 (77.39%) did engage in NSSI within the past month, and 78 of 116 (67%) reported that they had made an attempt to take their life. Youth who reported that they had attempted suicide (lifetime) reported significantly less difficulty with emotion regulation than youth who engaged in NSSI only, or both NSSI and suicide attempts. Conclusions: These youth reported a very high prevalence of self-harm, and in general substantial difficulty with regulating their emotions, and difficulty with their interpersonal relationships. The psychosocial distinctions evident between groups may have practical utility.