Background: Mentalization-Based Treatment (MBT) is a promising, though expensive treatment for severely ill patients with Borderline Personality Disorder (BPD). A high burden of disease in terms of quality of life (QoL) and life years lost can be a reason to prioritize mental health interventions, and specifically for BPD patients. Moreover, when the societal costs of the illness are high, spending resources on high treatment costs would be more easily legitimized. Therefore, the purpose of this study was to calculate the burden of disease of BPD patients eligible for MBT. Methods: The 403 patients included in this study were recruited from two mental health care institutes in the Netherlands. All patients were eligible for MBT. Burden of disease consisted of QoL, measured with the EuroQol EQ-5D-3L, and costs, calculated using the Trimbos and Institute for Medical Technology Assessment Questionnaire for Costs Associated with Psychiatric Illness. Results: The mean QoL index score was .48. The mean total costs in the year prior to treatment were (sic) 16,879 per patient, of which 21 % consisted of productivity costs. Conclusions: The burden of disease in BPD patients eligible for MBT is high, which makes it more likely that society is willing to invest in treatment for these patients. However, this finding should not be interpreted as a license to unlimitedly use resources to reimburse treatment for severe BPD patients, as these findings do not provide any information on the effectiveness of MBT or other available treatment programs for BPD. The effectiveness of available treatments should be evident by studies on the effectiveness of the treatment itself and by comparing the effectiveness of these treatments to treatment as usual and to other treatment options for BPD patients.