The OCI-R is a psychometrically sound and valid self-report scale measuring the major symptoms of OCD on six dimensions: Checking, Washing, Ordering, Hoarding, Obsessing, and Neutralizing. Information is needed on its ability to discriminate OCD from depression. In this study, reliability and convergent, divergent, and known-groups validity of an authorized German version were examined in 381 patients with OCD, other anxiety and depressive disorders. Confirmatory factor analyses replicated the original six-factor structure in each sample. Moreover, results indicated good convergent, divergent, and known-groups validity for the full scale and the subscales in each sample, only a slight construct overlap between OCD and depression, anxiety, pathological worry, and perfectionism, and the relationships of the subscales with obsessive-compulsive personality features supported its construct validity. Previous findings for the original scale were replicated and extended in a different cultural context. However, the domains Neutralizing and Obsessions need further development.