Symptoms of post-traumatic stress disorder are common in fibromyalgia patients. This study compared post-traumatic stress disorder symptoms in fibromyalgia patients and healthy controls and determined whether patient-control differences in post-traumatic stress disorder symptoms mediated differences in mental health. In all, 30 patients and 30 healthy controls completed questionnaires assessing symptoms of post-traumatic stress disorder and mental health. Fibromyalgia patients had greater symptoms of post-traumatic stress disorder and mental health than controls. Patient-control differences in mental health symptoms were fully or partially mediated by differences in post-traumatic stress disorder symptoms. Healthcare providers should understand the role of trauma as management of trauma symptoms may be one strategy for improving mental health.