Non-suicidal self-injury (NSSI) refers to self-inflicted physical injury without suicidal intent. NSSI is particularly common in forensic settings and associated with several psychosocial concerns, coping responses, diagnoses, and functions, but little information is available regarding NSSI in adjudicated male adolescents. The present study examined the frequency and types of NSSI among adjudicated male adolescents (n = 103) and assessed the relationships between NSSI history, psychosocial concerns, coping responses, diagnoses, and functions within this population. Approximately two-thirds (66%) reported NSSI history. Participants with NSSI history reported poorer social adaptation and greater alienation and boredom, aggression, and emotional lability than controls. Youth with high-frequency NSSI were also more likely to utilize emotional discharge as an unhealthy coping response than controls. In addition, participants with high-frequency NSSI were more likely than controls to meet criteria for a mood or anxiety disorder. Function of NSSI primarily surrounded anxiety reduction/affect regulation, punishment, dissociation reduction, and social/sensation-seeking. NSSI appears to be prevalent among male adjudicated youths, and the findings suggest that the relationship between NSSI history, psychosocial concerns, coping responses, and functions is nuanced and could inform more calibrated assessment and treatment strategies.