The aim of the present study was to investigate transdiagnostic role of repetitive negative thoughts, emotional dysregulation, intolerance of uncertainty, cognitive fusion and distress intolerance in depression and anxiety disorders. This study was causal-comparative. 149 patients with depression and anxiety disorders (included 37 patients with Major Depressive Disorder, 35 patients with Obsessive-Compulsive Disorder, 40 patients with Generalized Anxiety Disorder, 37 patients with Social Anxiety Disorder) selected by convenience sampling from eight psychiatric and psychological centers in Tehran. Then they compared with normal group (N=40) through Repetitive Negative Thoughts Questionnaire (RNTQ), Cognitive Fusion Questionnaire (CFQ), Difficulties in Emotion Regulation Scale (DERS), Intolerance Uncertainty Scale (IUS) and Distress Tolerance Scale (DTS). Data was analyzed using multivariate analysis of variance (MANOVA), ANOVA and Bonferroni tests. The results showed that participants in clinical groups weren’t together significant differences of repetitive negative thoughts, cognitive fusion and intolerance distress, but with normal groups were different. In addition, despite the fact that scores of intolerance of uncertainty in group of major depressive disorder was higher than normal group, but lower than anxiety disorders groups. In connection with the emotional dysregulation, results showed that only participants of group of major depressive disorder and generalized anxiety disorder were not different. Repetitive negative thoughts, cognitive fusion and intolerance distress are common transdiagnostic processes and play important role in development and maintenance in different depression and anxiety disorders.