Objectives. The aim was to validate the short PTSD-8 scale against the Structured Clinical Interview (SCID-1) for post-traumatic stress disorder and to test the latent structure of post-traumatic stress disorder in chronic pain patients. Methods. A total of 51 chronic nonmalignant pain patients exposed to a traumatic event were consecutively recruited from a multidisciplinary pain center. All participants answered a baseline questionnaire followed by the PTSD-8 and the diagnostic interview for PTSD. Finally, the latent structure of PTSD-8 was tested in a large cohort of 419 patients with chronic nonmalignant pain using confirmatory factor analysis (CFA). Results. In total, 33.3% had a diagnosis of PTSD. A good overall accuracy was found validating the PTSD-8 against the diagnostic interview. Convergent validity was indicated as the PTSD-8 correlated strongly with scores of depression and anxiety. The results of the CFA for the PTSD-8 three-factor structure provided excellent fit for the eight post-traumatic stress disorder symptoms. Conclusions. Overall, the results showed that the PTSD-8 is a valid short screening tool to assess possible post-traumatic stress disorder among patients with chronic pain. In addition, the PTSD-8 scale comprises all of the upcoming ICD-11 posttraumatic stress disorder symptoms within its eight items. Thus, the PTSD-8 is likely also to measure the proposed ICD-11 post-traumatic stress disorder.