This paper tests the hypothesis that the association between childhood maltreatment and adult personality dysfunction is at least partially attributable to insecure attachment, that is that attachment style mediates the relationship between childhood maltreatment and adult personality dysfunction. Associations between childhood trauma, as measured by the Childhood Trauma Questionnaire (CTQ), anxious and avoidant attachment in romantic relationships, as measured by the Experiences in Close Relationships-Revised (ECR-R), and five personality domains, as measured by the Severity Indices of Personality Problems (SIPP-118), were examined in a sample of 72 psychiatric inpatients. The SIPP-118 domains included relational capacities, identity integration, self-control, responsibility, and social concordance. The direct effect of childhood trauma on all SIPP-118 domains was not significant after controlling for the indirect effect of attachment. In regression modeling, a significant indirect effect of childhood trauma via adult attachment style was found for SIPP-118 relational capacities, identity integration, self-control, and social concordance. Specifically, anxious attachment was a significant mediator of the effect of childhood trauma on self-control, identity integration, and relational domains. These results suggest that childhood trauma impacts a broad range of personality domains and does so in large part through the pathway of anxious romantic attachment style.