MicroRNAs are a class of evolutionarily small non-coding RNAs of 19 to 25 nucleotides in length, that represent one of the most exciting areas of current medical science as they can regulate a complex regulatory network of gene expression and physiologic processes including differentiation, proliferation and apoptosis in a highly context dependent fashion. Recently, their role in cardiovascular disease and in the regulation of cardiomyocyte size and function, in the action potential, in angiogenesis and in mitochondrial function was recognized. Importantly, they have been evaluated for their prognostic and diagnostic role in heart failure and modification of specific microRNAs levels has been tested as a therapeutic option in experimental heart failure models. In this review article we refer the most emerging evidence, concerning the role of microRNAs in myocardial development in heart failure pathophysiology and prognosis, and their therapeutic implications.