There is a clear need to improve the measurement of posttraumatic symptoms in veterans seeking trauma-focused treatment. We evaluated the structure and psychometric performance of the Posttraumatic Stress Disorder (PTSD) Checklist for the Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition (PCL-5) in a naturalistic sample of veterans engaging in evidence-based therapy in a Veterans Affairs (VA) PTSD outpatient clinic. We collected data from 500 sequential patients at the beginning and end of treatment, evaluating the PCL-5 factor structure followed by psychometric analyses. Results align with recent research following rigorous methods and advanced statistical techniques in suggesting a unidimensional factor structure for the PCL-5, with indications for its items representing a general factor with no clear support for multiple factors or subscales aligned with specific symptom clusters. In addition, psychometric analyses suggest a wider range of potential cutoff scores predicting PTSD diagnosis that may be specific to this population or setting. Given the remaining research questions surrounding the PCL-5 and its structure and functioning specifically, as well as the evolving conceptualizations of PTSD as a psychological disorder, further research is needed to guide clinical practice and future research. (PsycInfo Database Record (c) 2023 APA, all rights reserved).