Mentalizing, the mental capacity to understand oneself and others in terms of mental states, has been found to be reduced in some mental disorders such as Borderline Personality Disorder (BPD). Some studies have suggested that Eating Disorders (EDs) may also be associated with impairments in mentalizing, but studies have not always yielded consistent results. This is the first study to systematically investigate mentalizing impairments in patients with Bulimia Nervosa (BN) compared with controls. In addition, we investigated whether impairments in mentalizing were related to BPD features, rather than BN per se, given the high comorbidity between BPD and BN.