MicroRNAs (miRNAs) are non-coding single-stranded RNAs with about 21˜ 23 nucleotides in length, which originate from encoding genes in nucleus. In most cases miRNAs play an inhibitory role in gene expression in a posttranscriptional level by partially complementary binding to the 3 unstranlated region (UTR) of target mRNAs. Large bodies of evidence have shown that miRNAs were involved in various diseases, such as cancer, infectious diseases, diabetes etc, and rising as critical modulators of pathological processes. Lately, some highlight articles revealed that the altered expression of miRNAs such as miR-1, miR-133, miR-21, miR-208 etc in hearts also contributed to cardiovascular diseases, such as heart ischemia, cardiac hypertrophy, and arrhythmias. Moreover, miRNAs are also identified to regulate heart development. These exciting findings not only improve our understanding of the molecular mechanisms of heart diseases, but also provide a new class of potential molecular targets— miRNAs, for the development of novel agents to treat heart diseases. Here, we summarized the recent discoveries about the role of miRNAs in cardiac physiological and pathological functions, and then discussed about their therapeutic potentials for heart diseases.