MicroRNAs (miRNAs) are small noncoding RNAs that block translation or induce degradation of mRNA and thereby control patterns of gene expression. Acute myocardial infarction is a common cardiovascular event that results in cardiac remodelling and can consequently lead to the development of chronic heart failure. Several miRNAs have been shown to control important processes that contribute to the pathophysiological consequences of acute myocardial infarction. miRNAs can either promote or inhibit cardiomyocyte cell death, and also regulate postischaemic neovascularization. Cardiac regeneration can also be regulated by miRNAs that control cardiomyocyte proliferation or interfere with cardioprotective effects mediated by stem or progenitor cells. miRNAs can also be used for direct reprogramming of cardiac fibroblasts into cardiomyocytes. In this Review, we focus on the current understanding of the role of miRNAs in these processes, and particularly discuss the therapeutic potential of miRNAs in treating acute myocardial infarction.