Background: Evaluation of treatment programs in addiction field is a prerequisite to improve the quality of care. This study aimed to investigate the effectiveness of Therapeutic Community (TC) program in Iran. Methods: Individuals who had voluntarily enrolled in the TC center within a period of seven years, from early 2005 to late 2011, entered the study. Those who successfully completed the 14-week residential course were considered as ‘completers’. They were subsequently called in for urine test and interviews using Maudsley Addiction Profile. Urine test was conducted to determine if they were positive for heroin, opium, methadone, methamphetamine, bupronorphine, hashish, and tramadol. Results: A number of 378 individuals with mean (±SD) age of 32.5 ± 7.8 enrolled in the TC program during the study period, 240 individuals of whom completed the 14 weeks course (69.0%). At the end of the sixth year, 22% of the participants were in abstinence. Physical and mental health in abstainers proved to be of better conditions than those of non-abstainers (P<0.05). Conclusion: Considering the TC outcome in other countries, it seems that TC maintains an acceptable effectiveness in Iran. Prospective controlled studies are warranted to investigate the outcomes in more details.