Circular RNAs (circRNAs) are a class of noncoding RNA molecules formed by the back splicing process. Compared to linear mRNA molecules they are more stable. CircRNA acts as miRNA sponges, regulates translation, epigenetic alterations, etc. However, the most significant aspect of circRNAs has been its role in regulating the hallmark of cancer and diabetes mellitus. Several circRNAs are extensively expressed in individuals with cancer and diabetics. Dysregulated expression of various circRNAs plays a crucial part in the development of type 2 diabetes mellitus. In the present review, we present the current understanding of cricRNAs biogenesis, regulatory mechanisms, reviews of recent findings and circRNA as potential biomarker.