The purpose of the present study was to assess posttraumatic stress disorder (PTSD), cognitive function, and quality of life in patients with schizophrenia who had a self-reported history of trauma exposure. Outpatients diagnosed with schizophrenia or schizoaffective disorder were referred to the study. Each patient was assessed with the Positive and Negative Syndrome Scale (PANSS), the Harvard Trauma Questionnaire (HTQ), a cognitive assessment battery, Heinrich's Quality of Life Scale (QLS), and the Behavior and Symptom Identification Scale (BASIS). Eighty-seven subjects who reported experiencing at least one traumatic event were included in the study. Fifteen of 87 (17%) met the DSM-IV criteria for PTSD. The PTSD group had significantly worse overall cognitive performance than the non-PTSD group, especially in the domains of attention, working memory and executive function. In addition, the PTSD group showed significantly worse self-rated quality of life as measured by the BASIS total score. The development of PTSD is associated with poor cognitive function and subjectively, but not objectively, rated low quality of life in patients with schizophrenia. Evaluating PTSD in patients with schizophrenia could have important implications from both clinical and research perspectives.