Dual antiplatelet therapy (DAPT), with aspirin plus a P2Y12 inhibitor agent, is the cornerstone treatment after percutaneous coronary intervention for acute coronary syndrome. Based on randomized clinical trial using aspirin and clopidogrel, a DAPT duration of 12 months has been recommended after an acute coronary syndrome. Despite the development of more potent antiplatelet agents (i.e. prasugrel and ticagrelor) and the reduction in ischemic recurrences after acute coronary syndrome, 12 months DAPT currently remains the gold standard. However, a significant proportion of patients experience recurrent ischemic events beyond the first 12 months after an acute coronary syndrome. Meanwhile, with more effective antiplatelet agent, bleeding has become a major safety concern on DAPT. Therefore, the ischemic and bleeding risk balance is central considering the duration of DAPT after an acute coronary syndrome. This review aims to report the evidence for an optimization and individualization of DAPT duration after an acute coronary syndrome.