Abstract: Introduction: Childhood traumatization plays a significant role in the etiology of borderline personality disorder. Studies found a significant association between childhood traumatization, dissociation, and nonsuicidal self-injurious behavior. Aim: The aim of our study was to assess dissociation and nonsuicidal self-injury among borderline inpatients and to reveal the association between childhood traumatization, dissociation, and self-injurious behavior. Method: The sample consisted of 80 borderline inpatients and 73 depressed control patients. Childhood traumatization, dissociation and self-injurious behavior were assessed by questionnaires. Results: Borderline patients reported severe and multiplex childhood traumatization. Cumulative trauma score and sexual abuse were the strongest predictors of dissociation. Furthermore, we have found that cumulative trauma score and dissociation were highly predictive of self-injurious behavior. Conclusion: Our results suggest that self-injurious behavior and dissociation in borderline patients can be regarded as indicators of childhood traumatization. Orv Hetil. 2017; 158(19): 740–747.