This report supports validation for the Spanish 18-item short version of the Inventory of Personality Organization (IPO), a self-reported instrument for the assessment of personality organization, according to Kernberg’s object-relation based model. The IPO is used to depict personality structure types, using three scales: psychological defense mechanisms, degree of identity integration and reality testing. The review of the literature suggests alternatively factorial solutions. Accordingly, this study, using a nonclinical sample (N = 315), tested the fit of several factorial models (2- and 3- factor solution) via the maximum likelihood approach. Confirmatory Factor Analysis revealed a better fit for the 2-factor solution (CFI =.97, TLI =.96, RMSEA =.037, AIC = 311.06), in accordance with Kernberg’s theory. Each of the 2 IPO subscales shows good levels of internal consistency, and they are associated with increased negative affect, aggressive dyscontrol as well as depression, anxiety and general level of psychopathological distress in line with theoretical expectations. Our results suggest that the Spanish short version of the IPO is a reliable and valid tool for the assessment of personality organization following Kernberg’s model.