The borderline personality disorder (BPD) is very complex psychopathologically and one of the psychological problems most difficult to treat. One of the treatment programs that has demonstrated to be effective empirically is Dialectical Behavior Therapy (DBT). BPD is often encountered as a comorbid condition in eating disorders what is usually a factor of worse prognosis. The aim of the present study is to offer preliminary evidence of the efficacy of DBT in two cases with a diagnosis of BPD and bulimia nervosa after one year of treatment. The results of this study showed decreases in desadaptative behaviours to regulate affect, substance abuse, self-mutilation behaviors, depressive symptoms (BDI-II), emotional eating (EES), number of hospitalizations, lower scores in global impairment and severity rated by the clinician, and higher scores in global assessment of functioning (Axis V, DSM-IV-TR). These preliminary data showed the possible efficacy of DBT to treat patients with severe BPD and eating disorders.