Gastrointestinal malignancies are a major cause of morbidity and mortality worldwide. Most cases are diagnosed at an advanced stage and, as such, 5-year survival rates are poor. MicroRNAs (miRNAs) are short, noncoding RNAs that negatively regulate gene expression at a post-transcriptional level. It is now evident that miRNAs are essential for normal physiological functioning, and aberrant miRNA expression is a hallmark of human cancers, including gastrointestinal cancers. Initially seen as a very promising source of breakthroughs in cancer management, there has been little translation of miRNA science from the bench to the bedside. This review will summarize the role of miRNAs in the pathogenesis of gastrointestinal malignancies. Further, it will serve to highlight the potential role of miRNAs in cancer prevention: namely their use as biomarkers and as targets for chemoprevention.