This study investigated the relative efficacy of Mentalization‐based therapy (MBT) and United Protocol (UP) in reducing symptoms of psychopathy and emotion dysregulation in a sample of Iranian community residents with concurrent diagnoses of antisocial and borderline personality disorders (PDs). Interpersonal, affective, and lifestyle features of psychopathy were measured post‐treatment and at 6‐, 12‐, 18‐, 24‐, and 36‐months follow‐up using the 13‐item version of the Psychopathy Revised‐Checklist (PCL‐R), which excluded, by design, criminal history features. Emotion dysregulation was measured using the Deficits in Emotion Regulation Scale (DERS) developed by Gratz and Roemer (2004). After treatment, both UP‐ and MBT‐treated individuals showed significantly fewer features of psychopathy and significantly less emotion dysregulation. Compared with those treated with MBT, UP‐treated individuals showed significantly less emotion dysregulation in all DERS subscales and a greater reduction in psychopathy features, particularly affective features. It is suggested that this likely reflected the particular emphasis placed by UP on improving emotional self‐regulation and facilitating the therapeutic alliance. These results suggest that, despite the traditional pessimism that surrounds psychopathic individuals' treatability, they can be successfully treated.