Objectives: The aim of the present study was to investigate the mediating role of cognitive fusion in the relationship of emotional dysregulation with anxiety and depression. Method: 543 students from Tehran University completed Cognitive Fusion Questionnaire (CFQ), Difficulties in Emotion Regulation Scale (DERS), Beck Anxiety Inventory (BAI) and Beck Depression Inventory-II (BDI-II). The data were analyzed using Pearson correlation and hierarchical multiple regression analysis. Results: All variables were correlated with each other significantly (p<0.001). The hierarchical multiple regression analysis showed that cognitive fusion has a complete mediating role in the relationship between emotional dysregulation and intensity of anxiety (ß= 0.84, p<0.001) and depression (ß= 0.79, p<0.001). Also Sobel’s test results confirmed the mediating role of cognitive fusion for anxiety (z=6.35, p<0.0001) and depression (z=5.11, p<0.001) Conclusion: Cognitive fusion is a mediating variable in the relationship between emotional dysregulation with anxiety and depression. When this variable is controlled, the relationships between emotional dysregulation with anxiety (ß=0.09, p>0.05) and depression (ß=0.07, p>0.05) are no longer significant.