Disasters can be an unpredictable source of complex 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 distressing symptoms that might not meet criteria for a specific disorder. Over 12-13 sessions, the CBT-PD program provides psychoeducation about PTSD and the broad range of psychological reactions to a disaster, and teaches core skills that empower clients to take charge of their recovery: breathing retraining (to reduce hyper-arousal 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 twenty 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 and worksheets that mental health providers can use with their clients.