This guide provides mental health professionals with a detailed understanding of the biopsychosocial nature of gambling disorder and shares current theories, interventions, and evidence-based strategies for use in clinical practice. It offers guidance for working with individuals of all ages and covers different gambling styles, activities, and subtypes, including new forms of gambling through online and virtual platforms. Based on the extensive experience of the authors working with and researching gambling addiction, it examines how treatment can be tailored for specific client groups, including trauma survivors, military personnel, the elderly, adolescents, and diverse communities. It provides detailed diagnostic and screening resources and includes important information on financial and legal issues. It is essential reading for any therapist treating clients with gambling disorder.