The present study was conducted to investigate the the effectiveness of unified trans-diagnostic treatment on cognitive fusion and resilience of victims of bullying students. The research method was semi-experimental with a pre-test and post-test design with a control group and a 2-month follow-up phase. The statistical population was formed by male students who were victims of bullying in the first year of secondary school in Najafabad city (Goldasht city) in the academic year of 2021-2022. The research sample consisted of 35 male students who were victims of bullying, who were selected in a purposeful way and randomly assigned to two experimental and control groups (18 students in the experimental group and 17 students in the control group). Then, the experimental group received an unified trans-diagnostic treatment intervention for 10 weeks in a weekly session of 90 minutes. The applied questionnaires in this study included Bullying Victim Questionnaire (BVQ), Cognitive Fusion Questionnaire (CFQ) and Resilience Questionnaire (RQ). The results showed that unified trans-diagnostic treatment has significant effect on the cognitive fusion (p<0001, Eta=0.62, F=55.74) and resilience (p<0001, Eta=0.62, F=54.82) of the cognitive fusion and resilience of victims of bullying students. According to the findings of the present study it can be concluded that unified trans-diagnostic treatment can be used as an efficient method to decrease cognitive fusion and increase resilience of victims of bullying students through Identifying emotions, teaching emotional awareness, cognitive re-evaluation, identifying patterns of avoiding emotions and examining behaviors caused by emotions.