Purpose: The aim of the research was to investigate the effectiveness of mindfulness-based on cognitive therapy on intolerance of uncertainty, extreme sense of responsibility and thought _ action fusion in women suffering from obsessive-compulsive disorder in Arak.

Method: The research method was quasi-experimental with pre-test-post-test design and experimental and control groups.The present statistical population included all patients with obsessive-compulsive disorder in Arak who referred to counseling clinics in 1400. The sampling method was purposive. Thirty women with obsessive-compulsive disorder were selected from counseling centers in Arak based on their psychiatric records and clinical interviews and were randomly assigned to experimental and control groups (15 people in each group). The research instruments were the obsessive-compulsive review questionnaire of Foa et al. (2000), the Freeston et al. (1994) Doubt Tolerance Scale, the Salkovskis et al. (2000) Responsibility Attitude Questionnaire, and the Schaffran et al. Which was performed on the experimental group in two stages of pre-test and post-test. Cognitive therapy based on Segal et al. (2013) mindfulness therapy was performed in 8 sessions of 90 minutes once a week. The control group waited for treatment after the intervention after the pre-test. The data were analyzed using SPSS software and covariance analysis.

Findings: The results showed that mindfulness-based cognitive therapy has a significant effect on intolerance of uncertainty, extreme responsibility and confusion of thought and action in patients with obsessive-compulsive disorder (P <0.0001).