Maternally expressed gene 3 (MEG3) is an imprinted gene located at the imprinted DLK1-MEG3 locus in chromosome 14q32.3. MEG3 is a long noncoding RNA (lncRNA) and it expresses aberrantly in tumor tis-sues. MEG3 plays a vital role in the genesis and development of tumor via multiple mechanisms. In this review, we fo-cus on the mechanisms of MEG3 in tumor.