Multiple Sclerosis (MS) is a severe and chronic inflammatory disorder of the central nervous system in which clinical manifestations and extreme neurological disabilities are presented. Acceptance and Commitment Therapy (ACT) is a third wave treatment option used in medical populations to help patients cope with the physical stress of diseases. The present study aimed to evaluate the effectiveness of Acceptance and Commitment Therapy (ACT) on disease acceptance and eexperiential avoidance in patients suffering from multiple sclerosis (MS). The population of this study included all patients suffering from multiple sclerosis (MS) in East Azerbaijan province in 2016. Among them, 30 patients referred to the MS Society were selected through purposive sampling and then randomly assigned into two experimental (n=15) and control (n=15) groups. The experimental group received 10 sessions of ACT intervention. Multiple Sclerosis Acceptance Questionnaire (MSAQ) and the second version of the Acceptance and Action Questionnaire (AAQ-ii) were used as data collecting tools.  Analysis of variance combined with mixed-design repeated measures (ANOVA) was used and data was analyzed using SPSS₂₁ software. The findings of the study revealed that the score of disease acceptance both in post-test and in follow-up increased significantly in the experimental group. Thus, it is important to pay attention to psychological and physical problems in this clinical population. Furthermore, it would be beneficial to offer, along with medication, psychological treatments including ACT to these patients.