Studies have reported that adherence to medications after hospital discharge for myocardial infarction is poor with about 12% to 20% of patients discontinue their medications six months after discharge. This study aimed to examine the effect of self-efficacy enhancement program on medication adherence in post-acute myocardial infarction patients.A total 44 patient with post-acute myocardial infarction were recruited from the in-patient department, Police General Hospital. The participants were random assigned into control group and experimental group. The control group received conventional care while the experimental group attended a four-week self-efficacy enhancement program, which included motivation, skill practice, and monitoring skills. The mean self-efficacy score between groups was assessed. The pill count was used to measure medication adherence. Correlations between self-efficacy and medication adherence were examined. Data were analyzed using descriptive statistic, Pearson's correlation, and t-test.The mean score on medication adherence of the experiment group who attended the self-efficacy enhancement program was significantly greater than the control group (t=−2.77; df=21; p=0.01). The mean scores of self-efficacy between the experimental and control group were 35.73 (SD=4.11) and 35.41 (SD=3.78). The correlations between self-efficacy and medication adherence were significantly (r=1.00, p=0.00).The effectiveness of self-efficacy enhancement program was effective in improving medication adherence in Thai post-acute myocardial infarction.