Book excerpt: This handbook provides mental health professionals with a thorough understanding of the biopsychosocial nature of disordered gambling and shares current evidence-based theories, interventions and strategies to use in clinical practice. It provides guidance for working with individuals of any age and covers different gambling modes, activities and subtypes, including new forms of gambling through online and virtual platforms. Drawing on the authors' substantial experience working with and researching gambling addiction, it considers how treatment can be specialized for particular client groups, including trauma survivors, military, older adults, adolescents and diverse communities. It provides detailed diagnostic and screening resources and includes important information on the financial and legal aspects. This is essential reading for any therapist treating clients with gambling disorder.