Introduction: The Borderline Personality Inventory (BPI) is based on Kernberg’s concept of borderline personality organization and DSM-IV diagnostic criteria. The BPI contains scales for assessing identity diffusion, impaired primitive defense mechanisms, reality testing, and fear of closeness. The aim of this study was to investigate the validity of this scale.Method: We conducted the study in a survey and cross sectional context. Using a stratified random sampling method, 411 normal participants were selected for the study. Participants answered the BPI and the Borderline Personality Scale. Data were analyzed using explanatory factor analysis of variance and Pearson’s correlation methods.Results: Principle component analysis with promax rotation extracted four factors labeled identity diffusion, primitive defense mechanisms, impaired reality testing, and fear of closeness. However two other types of validity (convergent validity and inter-correlations between subscales and the whole scale) and three reliabilities (test retest, split half and internal constancy) have been reported for this scale.Conclusion: The findings were similar to the results of previous studies. It was concluded that the BPI has good validity and reliability in an Iranian population, and that it can be used as valid measure in borderline personality studies.