Background: Studies shows that women who have been unfaithful to their husbands suffer from symptoms of depression and rumination, research has also shown the efficacy of Acceptance and Commitment Therapy (ACT) on depressive symptoms and rumination. therefore according to the research background, there was a research gap in the field of acceptance and commitment therapy (ACT) on rumination and depressive symptoms in women after infidelity. Aims: The aim of this study was to evaluate the efficacy of Acceptance and Commitment Therapy (ACT) on women who experienced symptoms of depression and rumination. Methods: The method of the present study was quasi-experimental with a pretest-posttest design and follow-up with a control group in women affected by infidelity. The population of this study was 73 women affected by infidelity in the eastern suburbs of Tehran who referred to the resuscitation group therapy center of the heart and answered the Nolan Hoxma (2003) Ruminant Ruminant Questionnaire and the Beck Depression Inventory (1996). Out of 73 participants, 30 participants were selected in two groups of 15 people (control and experimental) who met the criteria for entering the study and were randomly divided into two groups. The experimental group received 8 sessions of 90-minute Acceptance and Commitment Therapy (ACT). Finally, after the post-test, the results were analyzed by repeated measures analysis of variance. Results: Findings showed that after the end of follow-up, the results of the experimental group in both depression and rumination variables were significantly different in post-test and follow-up test, but this difference was not observed between the control group in three stages (P> 0.05). Conclusion:Considering that acceptance and commitment therapy is effective in reducing rumination and depressive symptoms such as unpleasant and repetitive thoughts, inefficiency of current behavior as well as accepting the problem and creating a gap between current thoughts and practice in women affected by infidelity, it can be He did it on more examples and in a society with a different culture.