The present study aimed to examine the effectiveness of dialectical behavior therapy (DBT) on nonsuicidal self-injurious behaviors and executive functions in individuals diagnosed with borderline personality disorder (BPD). This research followed a quasi-experimental design with pre-test, post-test, and a control group. The statistical population included all individuals with BPD who referred to counseling centers or psychiatric clinics in Shahrud during 2022. A total of 40 participants were selected using convenience sampling and randomly assigned to experimental and control groups (20 each). In the pre-test phase, participants completed the Barkley Executive Functioning Questionnaire (2011) and the Klonsky & Glenn Self-Injury Inventory (2009). The experimental group received eight sessions of DBT based on the protocol by Neacsiu et al. (2010), while the control group received no intervention. The results showed that DBT significantly improved various aspects of executive functioning, including time management, problem-solving, self-control, and emotional regulation. Additionally, DBT significantly reduced interpersonal nonsuicidal self-injury behaviors, though no significant effect was observed on intrapersonal self-injury. Follow-up results indicated that the effect on self-control remained stable over time. Overall, the findings confirm the effectiveness of DBT in enhancing cognitive and emotional regulation and in reducing harmful behaviors in patients with borderline personality disorder. Therefore, it is recommended that DBT be employed as a clinical intervention for this population.