Abstract: Circular RNAs (CircRNAs), as special non-coding RNAs, are novel closed-loop RNA molecules that are formed from pre-mRNAs by reverse splicing. The rapid development of biotechnology and increasing research have led to new insights into the identification and function of CircRNAs. CircRNAs have been considered to be untranslatable into proteins because of the lack of a 5' cap structure. However, some evidence has revealed that they can encode polypeptides via the internal ribosomal entry site and N6-methyladenosine (m⁶A) induction and can play an important role in the biological behavior of various malignancies. Thus, in this review, using domestic and international research literature, we summarized the possible mechanisms of peptide translation by CircRNAs, assessed the functions and effects of peptide products in common malignant tumors, and discussed their possible problems and potential clinical applications.