This article aims to identify different personal characteristics in treatment-responsive and treatment-resistant perpetrators of intimate partner violence who completed a batterer intervention program (BIP). The sample consists of 105 perpetrators of intimate partner violence who were court-mandated to a community-based cognitive behavioral program. Perpetrators were classified by professionals as resistant or responsive to treatment based on the stage of change they reached upon completion of the program. The results show that before starting the intervention program, treatment-resistant perpetrators scored higher than treatment-responsive perpetrators in external responsibility attributions and attitudes toward violence in intimate relationships. No differences were found in personality disorders or psychological symptoms between the groups. However, longer program participation correlates with increasing differences between the two groups. The results suggest that targeting the personal characteristics which differentiate treatment-responsive perpetrators from treatment-resistant ones may help to increase the efficacy of BIPs.