Although >85% of the human genome is transcribed, only <2% is transcribed into protein‐coding RNA (messenger RNA, mRNA). Many thousands of noncoding RNAs are transcribed and recognized as functional RNAs with diverse sizes, structures, and biological functions. Based on size, noncoding RNA can be generally divided into two subgroups: short noncoding RNA (<200 nucleotides including microRNA or miRNA) and long noncoding RNA (lncRNA, >200 nucleotides). It is now clear that these RNAs fulfil critical roles as transcriptional and post‐transcriptional regulators and as guides of chromatin‐modifying complexes. Although not translated into protein, noncoding RNAs can regulate cardiac function through diverse mechanisms and their dysregulation is increasingly linked with cardiovascular pathophysiology. Furthermore, a series of recent studies have discovered that noncoding RNAs can be found in the bloodstream and some species are remarkably stable. This has raised the possibility that such noncoding RNAs may be measured in body fluids and serve as novel diagnostic biomarkers. Here, we summarize the current knowledge of noncoding RNAs’ function and biomarker potential in cardiac diseases, concentrating mainly on circulating miRNAs and lncRNAs. J. Cell. Physiol. 9999: 1–5, 2015. © 2015 Wiley Periodicals, Inc.