Cardiovascular disease is the leading cause of morbidity and mortality in developed countries. The pathological process of the heart is associated with an altered expression profile of genes that are important for cardiac function. MicroRNAs (miRNAs) have recently emerged as one of the central players of gene expression regulation. The implications of miRNAs in the pathological process of the cardiovascular system have recently been recognized, and research on miRNAs in relation to cardiovascular disease has now become a most rapidly evolving field. In this review, we focus on miRNAs and control of cardiac excitability, aiming to provide a comprehensive overview on the available experimental data on regulation of cardiac conduction, repolarization, and automaticity by miRNAs. Aberrant expression of miRNAs in the diseased state of the heart and their arrhythmogenic or anti-arrhythmic potential will be discussed. Finally, the innovative miRNA-interference technologies developed lately for manipulating the action of miRNAs by interfering with their expression, stability, and function as new approaches for miRNA research and gene therapy will be introduced.