The present study is a quasi-experimental study in which the effect of peer education on self-efficacy in patients with heart failure was investigated in 2016. The research environment of this study included Shahid Chamran and Shahid Modarres hospitals of Saveh county which were affiliated with the Arak University of Medical Sciences. In order to determine the sample size, according to the number of heart failure patients referring to these hospitals and according to the consultant professor’s view, the Cochran sample size determining formula was used for the limited community. Sixty Subjects from selected hospitals of Saveh county by the availability sampling method were selected for this study; these participants were patients with heart failure who had met inclusion criteria. The research data had been collected through two questionnaires: demographic data and self-efficacy. After preparing the peer group, during one month, four education sessions were conducted by peers for peer groups. After collecting the data, according to the research objectives, data were entered into SPSS software version 21 and were analyzed. In order to achieve specific objectives and answer research questions, descriptive statistics including tables and central tendency indexes such as average and indices of dispersion such as standard deviation and inferential statistics such as independent t-tests and chi-square were used. Results indicated that the highest percentage of the studied subjects before the intervention (53/8%) had low self-efficacy and the lowest percentage of them (6/6%) had high selfefficacy. The mean and standard deviation of self-efficacy in studied subjects before the intervention were23/4 and 0/58, respectively. In investigating the subjects after the intervention, it was found that most of them (56/7%) had high self-efficacy and lowest percentage of them (10%) had low self-efficacy. The mean score and standard deviation of self-efficacy in subjects after intervention were respectively 48/8 and 2/26. Research findings also showed that an before education average of 23/6 changed to after education average of 48/8 and paired t-test indicates that education had an impact on self-efficacy in patients. Result is that peer education would improve the self-efficiency of patients with heart failure.