Background: Epidemiologic studies have shown the relationship between glycemic control and coronary artery disease. We studied the effect of glycemic control on major adverse cardiovascular event (MACE) in patient with acute myocardial infarction and percutaneous coronary intervention (PCI). Methods: We reviewed 188 diabetic patients who underwent PCI with stent implantations due to acute myocardial infarct (AMI) including ST elevation and non-ST elevation myocardial. We measured the initial and follow-up glycosylated hemoglobin (HbA1c) level at 6 to 12 months from index PCI. Lower than 7.0% of HbA1c was defined to controlled diabetes. All subjects were divided into four groups according to the initial and follow-up HbA1c levels: group 1 as controlled to controlled diabetes (26.6%), group 2 as controlled to uncontrolled diabetes (12.2%), group 3 as uncontrolled to controlled diabetes (19.7%), and group 4 as an uncontrolled to uncontrolled diabetes (41.5%). MACE was defined composites of any death, myocardial infarct, target vessel revascularization and target lesion revascularization. Results: There was no difference in sex, diagnosis, killip classifications, culprit lesions, medical history and medications among groups. Age was significantly lower in initially uncontrolled diabetes groups (group 1: 64.4 짹 9.5; group 2: 62.0 짹 9.9; group 3: 60.0 짹 11.5; group 4: 58.9짹10.3; p = 0.026). Initial HbA1c and follow-up HbA1c level were significantly different by groups (Initial HbA1c, %,: 6.0 짹 0.6, 6.4 짹 0.3, 8.3 짹 1.4, 8.6 짹 1.4; p < 0.01; follow-up HbA1c, %: 6.0 짹 0.5, 7.8 짹 1.0, 6.3 짹 0.5, 8.6 짹 1.4; p < 0.01). There were no differences in MACE among four groups. In post-hoc analysis, MACE of group 2 (controlled to uncontrolled HbA1c) was significantly higher than group 1 (12.0% vs. 34.8%, p = 0.02). But, There was no difference in MACE between group 3 and 4 (21.6% vs. 23.6%, p = 0.86). Conclusion: Strict glycemic control is related to the clinical outcomes in well controlled diabetic patients at index PCI with AMI and stent implantations. However, glycemic control could not affect the clinical outcomes in case of poorly controlled diabetes and AMI with stent implantations.