Posttraumatic stress disorder (PTSD) is a chronic psychological disorder that can develop after exposure to a traumatic event. This review summarizes the literature on the epidemiology, assessment, and treatment of PTSD. We provide a review of the characteristics of PTSD along with associated risk factors, and describe brief, evidence-based measures that can be used to screen for PTSD and monitor symptom changes over time. In regard to treatment, we highlight commonly used, evidence-based psychotherapies and pharmacotherapies for PTSD. Among psychotherapeutic approaches, evidence-based approaches include cognitive-behavioral therapies (e.g., Prolonged Exposure and Cognitive Processing Therapy) and Eye Movement Desensitization and Reprocessing. A wide variety of pharmacotherapies have received some level of research support for PTSD symptom alleviation, although selective serotonin reuptake inhibitors have the largest evidence base to date. However, relapse may occur after the discontinuation of pharmacotherapy, whereas PTSD symptoms typically remain stable or continue to improve after completion of evidence-based psychotherapy. After reviewing treatment recommendations, we conclude by describing critical areas for future research.