Nonsuicidal self-injury (NSSI) is a baffling, troubling, and hard to treat phenomenon that has increased markedly in recent years. Key issues in diagnosing and treating NSSI adequately include differentiating it from attempted suicide and other mental disorders, as well as understanding the motivations for self-injury and the context in which it occurs. This accessible and practical book provides therapists and students with a clear understanding of these key issues, as well as of suitable assessment techniques. It then goes on to delineate research-informed treatment approaches for NSSI, with an emphasis on functional assessment, emotion regulation, and problem solving, including motivational interviewing, interpersonal skills, CBT, DBT, behavioral management strategies, delay behaviors, exercise, family therapy, risk management, and medication, as well as how to successfully combine methods.