The Five-Factor Obsessive–Compulsive Inventory (FFOCI) is a recently developed measure of obsessive–compulsive personality disorder (OCPD) based on an established dimensional model of general personality, the five-factor model. The present study aimed to evaluate the construct validity of the FFOCI by examining its associations with both traditional and dimensional diagnostic models of OCPD. This study used an archival data set of mental health patients that employed a multimethod design. A total of 214 individuals (and their nominated informants) completed various personality inventories indexing the Diagnostic and Statistical Manual for Mental Disorders–Fifth edition traditional and Alternative Model of Personality Disorders (AMPD) diagnostic criteria for OCPD, as well as other individual AMPD personality traits deemed conceptually relevant to the FFOCI. The results were generally quite supportive of construct validity. They showed that FFOCI scale scores converged with traditional measures of OCPD and AMPD–OCPD traits and impairment in a conceptually expected manner, with a few exceptions. Overall, it was clear from these findings that the FFOCI takes a broader and more comprehensive approach to the assessment of obsessive–compulsive than traditional Diagnostic and Statistical Manual and AMPD operationalizations.