Background Substance abuse is one of the most important problems nowadays that has found the world range. A disaster that destroys millions of lives, and big national funds are spent to fight or compensate its damages. Objectives This study was conducted with the aim of examining the effectiveness of mindfulness-based cognitive therapy on reducing smoking among addicts in Tehran. Methods The method used in this study in terms of the applied purpose and data collection, was quasi-experimental design with pretest-posttest group and control group. Statistical population of the present study consisted of all male smokers aged 20 to 40 years living in Tehran, who had been referred to the stop smoking clinic in Tehran municipality and Javanmardan park for treatment. Convenience sampling method was used to choose samples from statistical population. In this way, 30 persons who smoked cigarette daily were chosen and referred for treatment; they were randomly divided into one experimental group and one control group. Thus, 15 persons were randomly assigned to the control group and 15 ones to the experimental group (mindfulness). The Self-made questionnaire for smoking rate was used in this study. Using SPSS software, obtained data from questionnaires were analyzed and divided into two parts, descriptive and inferential. Results According to the obtained results, there was a significant difference between the experimental and control groups (P < 0.05).The results showed that mindfulness is effective in reducing smoking in the persons aged 20 to 40 years. Conclusions Based on the findings of this study, it can be stated that some solutions should be considered in order to conduct the mindfulness-based cognitive therapy in counseling centers.