Aims: Given the importance of quality of life among addicts for more effective treatment, this research was designed to assess the effectiveness of acceptance and commitment therapy on quality of life in patients undergoing methadone maintenance therapy.
Materials & Methods: The present study was a semi-experimental design with control group. The study population was all addicts under Methadone maintenance treatment (MMT) in addiction treatment clinics in Isfahan in 2017. Through cluster sampling, one center was selected. With target sampling 24 people were chosen, and divided randomly into control and experimental groups. Intervention based on acceptance and commitment was held to the experimental group for 8 sessions. The control group did not receive any intervention. Quality of life Questionnaire (WHOROL-BREF, 1996) was  used in both groups in pretest and post–test. Data analyzed by  spss software V-23, and One-variable covariance analysis.
Findings: ANCOVA analysis results showed the effectiveness of treatment in increasing the quality of life in the experimental group compared with the control group.
Conclusion: Acceptance and commitment treatment techniques is effective in quality of life of patients.