Disasters are an unpredictable source of complex and often urgent mental health issues. A mass casualty disaster occurs somewhere in the world on a near daily basis, and victims can have symptoms that persist over time. Cognitive behavior therapy for postdisaster distress (CBT-PD) is a transdiagnostic approach to the treatment of a range of problematic symptoms that might not meet criteria for a specific disorder. Over 12 to 14 sessions, the CBT-PD program provides psychoeducation about posttraumatic stress disorder (PTSD) and the broad array of psychological responses to disasters. It teaches core skills that empower clients to take charge of their recovery: breathing retraining (to reduce hyperarousal and anxiety), activity scheduling of pleasant and meaningful events (to reduce depression and avoidance of valued roles), and cognitive restructuring (to reduce negative feelings and change thoughts and beliefs that underlie persistent postdisaster reactions). Refined over 20 years of clinical practice, this research-based approach is associated with significant reductions in PTSD and other distressing symptoms. This practical guide includes therapist scripts and client vignettes, and over two dozen worksheets, assessment tools, and other clinical handouts that mental health providers can use with their clients. Online appendixes including worksheets, assessment tools, and handouts are available at the Clinician and Practitioner Resources section of the book's companion website (https://www.apa.org/pubs/books/treatment-for-postdisaster-distress).