Background: The recently published ICD-11 includes substantial changes to the diagnosis of posttraumatic stress disorder (PTSD) and introduces the diagnosis of Complex PTSD (CPTSD). The International Trauma Interview (ITI) has been developed for clinicians to assess these new diagnoses but has not yet been evaluated. Objectives: To evaluate the psychometric properties of the Swedish translation of the ITI by examining the interrater agreement, latent structure, internal consistency, and convergent and discriminant validity. Methods: In a prospective study, 186 adults who had experienced a potentially traumatic event were assessed with the ITI and answered questionnaires for symptoms of posttraumatic stress, other psychiatric disorders, functional disability, and quality of life (QoL). Results: The diagnostic rate was 16% for PTSD and 6% for CPTSD. Interrater agreement was satisfactory (α = .76), and confirmatory factor analysis indicated that a two-factor second-20 order model consistent with the ICD-11 model of CPTSD provided acceptable fit to the data. Composite reliability analysis demonstrated that the ITI possessed acceptable internal reliability, and associations with measures of other psychiatric disorders, insomnia, functional disability, and QoL supported the concurrent validity of the ITI. Conclusion: Swedish ITI shows promise as a clinician-administered instrument to assess and diagnose ICD-11 PTSD and CPTSD.