Nonsuicidal self-injury (NSSI) frequently co-occurs with eating disorders, especially bulimia nervosa (BN). Theoretical models and empirical evidence show many overlapping risk factors for the onset and maintenance of NSSI and BN. However, among those with BN, it remains unclear what distinguishes those who do versus do not engage in NSSI. The primary objective of the present study was to identify factors predicting NSSI among women with BN. Specifically, we tested four domains of borderline personality disorder as mediators between childhood trauma and NSSI.