Health beliefs have been shown to influence a myriad of medical treatment decisions. More recently, the impact of health beliefs on treatment decisions for mental illness has become a focus of study. This study examines the health beliefs and treatment behavior of veterans with posttraumatic stress disorder (PTSD). Using standard survey methodology, we assessed beliefs about the cause of PTSD, expected duration and controllability of symptoms, and life consequences of having PTSD. Treatment participation and medication compliance were assessed, as were common treatment correlates, such as patient-provider relationships, dosing frequency, side effect severity, number of prescribed medications, and use of drugs or alcohol to control PTSD symptoms. Explanatory models of PTSD, perceived controllability, and use of benzodiazepines were found to predict psychiatric medication use. Negative life consequences of PTSD were associated with participation in psychotherapy. Assessment of health beliefs may help providers to understand their patients’ treatment behavior and to facilitate treatment engagement.