This book is a practical guide to the evidence-based Cognitive Restructuring (CR) for PTSD program, which has been specifically designed to meet the unique needs of people with serious mental illness.  Posttraumatic stress disorder (PTSD) is very common among persons with serious mental illness (SMI). Unfortunately, it often leads to more severe psychiatric symptoms, greater impairment in psychosocial functioning, poorer physical health, and a higher use of acute care services among people with SMI. Yet despite major advances in the treatment of PTSD in the general population, PTSD has remained underdiagnosed and underaddressed among people with SMI, and treatments for this population have been relatively neglected. This practical, hands-on guide gives clinicians the tools they need for screening, detecting, and treating PTSD in their clients with SMI, including schizophrenia, bipolar disorder, major depression, and borderline personality disorder. Chapters summarize research and theory regarding the interaction between PTSD and SMI, provide nuts and bolts strategies for implementing the authors' Cognitive Restructuring for PTSD program, and offer guidance for overcoming clinical challenges to trauma treatment such as psychotic symptoms, low distress tolerance, emotion dysregulation, hopelessness, and cognitive impairment. Chapters also feature in-session dialogues with case vignettes that follow three unique clients as they participate in the CR for PTSD program. Handouts and worksheets for delivering the CR for PTSD program are available in the Appendix of the book as well as in printable versions online (https://www.apa.org/pubs/books/treatment-posttraumatic-stress-disorder-serious-mental-illness) under the Resources tab. These online resources also include the educational handouts and worksheets translated into Spanish, a supplemental chapter on The BREATHE Program: A Brief PTSD Intervention for Persons with SMI in Special Settings, and the BREATHE Treatment Program Manual.