Background: No-reflow phenomenon is a serious complication of percutnaneous coronary intervention (PCI) and associated with poor prognosis. We evaluated triple antiplatetet therapy could improve clinical outcomes in patients with acute myocardial infarction (AMI) who had no-reflow phenomenon during PCI compared with dual antiplatelet therapy. Methods: A total of 727 eligible patients enrolled in Korean Acute Myocardial Infarction Registry (KAMIR) received either dual antiplatelet therapy (aspirin and clopidogrel; dual group, n=532) or triple antiplatetlet therapy (aspirin, clopidogrel and cilostazol; triple group, n=195). The triple group received additional cilostazol at least for a month. Angiographic no-reflow phenomenon was defined as post-PCI Thrombolysis In Myocardial Infarction (TIMI) flow grade 0,1 and 2. We evaluated 1-year major adverse cardiac events (MACEs) including death, myocardial infarction (MI), target vessel revasculization (TVR) and coronary artery bypass grafting. Results: No difference was observed in baseline clinical characteristics. No difference was also observed in procedural characteristics except that the post TIMI flow grade 0 was more common in the dual group. The triple group had a similar incidence of major bleeding and in-hospital mortality compared with the dual group. At 1-year, the triple group had significantly lower cardiac mortality (17.7% vs. 11.8%, log-rank p=0.039), all-cause mortality (19.0% vs. 12.3%, log-rank p=0.035) and lower incidences of the composite of MACEs (25.9% vs. 16.9%, adjusted hazard ratio 0.56, 95% confidence interval 0.37 to 0.86, p=0.007) compared with the dual group with no differences in MI and TVR. In subgroup analysis, the beneficial effects of triple antiplatelet therapy was prominent in patients with female gender, old age, diabetes milletus, and post TIMI flow grade 0. Conclusion: Triple antiplatelet therapy is superior to dual antiplatelet therapy in patients with AMI who had no-reflow phenomenon during PCI, especially in elderly female patients with diabetes milletus and TIMI flow grade 0.