Background: The Clinician-Administered PTSD Scale (CAPS-5) is a structured diagnostic interview developed to diagnose post-traumatic stress disorder (PTSD) based on the criteria of the fifth edition of the Diagnostic and Statistical Manual of Mental Disorders. A first study investigating the psychometric properties and factorial structure of the German version of the CAPS-5 was conducted using data from previously-collected data to check the inclusion criteria for PTSD. The current study aimed to verify the robustness of the psychometric properties of the German CAPS-5 via validating it within a routine clinical context could help underlie the robustness Methods: Overall, 288 participants were recruited. A multi-trait/multi-method design was used to analyze the validity of the German CAPS-5. Furthermore, the internal consistency, test-retest reliability, inter-rater reliability, and diagnostic accuracy of the German CAPS-5 were investigated. Finally, a cut-off score for the German CAPS-5 was calculated using ROC analyses. Results: The study showed good to excellent internal consistency, test-retest reliability, interrater reliability, construct validity, and diagnostic accuracy of the German CAPS-5. Finally, the study revealed a cut-off score for the German CAPS-5 sum score of ≥ 40. Discussion: The German CAPS-5 was found to be a structured diagnostic interview with good to excellent psychometric properties. The results revealed good convergent validity of the German CAPS-5, but more studies are needed into the divergent validity of the German CAPS-5. Trial registration: Trial ID: DRKS00015325 (https://www.drks.de)