Background : The prevalence of smoking among adolescents at age ≥15 years. That 34,8% in men and 2,7 in women. Efforts to improve the attitudes and knowledge of smoking in Mechanical Engineering University Students Muhammadiyah Yogyakarta 2015 needs to be done so that those who smoke have the wanted and the awareness to stop smoking is by forming Self Help Group (SHG). This study alms to determine the effect of the Self Help Group toword attitude smoking in Mechanical Engineering University Sstudents Humammadiyah Yogyakarta 2015. Methods : This study was a quasy-experimental study. The sample in this study used 52 students who smoked were divided into two groups, intervention and control gruop. This research was conducted in Mechanical Engineering University Students Muhammadiyah Yogyakarta 2015. The sampling technique used was random sampling method. Test analysis used Wilcoxon test and Mann-Whitney for attitude. Results : The analysis test showed there was a significant effect of Self Help Group (SHG) on attitude with p=0,000 (0,05). There was a differences on knowledge between intervention and control groups with p=0,000 (p<0,05). Conclusion : Self Help Group had a significant effect and different in improving the knowledge and attitude to stop smokingin the intervention and control groups on Mechanical Engineering University Students Muhammadiyah Yogyakarta 2015.