Abstract In recent years, the study of neuropsychology has played a significant role in explaining the symptoms of borderline personality disorder. Therefore, the purpose of this study was to model the relationship between cognitive defusion and problem-solving, considering the mediating role of metacognitive awareness in individuals with borderline personality disorder. The population of this research included all individuals with borderline personality disorder in Kurdistan province, aged between 18 and 60 years, during 2020 and 2021. A purposive sampling method was employed, following the "Kline" rule, and a total of 234 individuals were selected from this population. The participants completed the Cognitive Fusion Questionnaire by Gillanders et al. (2014), the Metacognitive Awareness Inventory by Schraw and Dennison (1994), and the Social Problem Solving Inventory by D'Zurilla and Nezu (2002). The data were analyzed using structural equation modeling in Amos-22 software. The results confirmed the mediating role of metacognitive awareness in the relationship between cognitive defusion and problem-solving abilities in individuals with borderline personality disorder. Specifically, cognitive defusion directly and positively influences problem-solving skills (p < 0.01, β=0.47), and metacognitive awareness also directly and positively affects problem-solving skills (p < 0.01, β=0.19). Additionally, cognitive defusion indirectly affects problem-solving skills by influencing metacognitive awareness (p < 0.05, β=0.07). These results highlight the significance of both cognitive defusion and metacognitive awareness in predicting and improving problem-solving abilities in individuals with borderline personality disorder.
