DNA methyltransferase inhibitors (or DNMT inhibitors) are a class of compounds that interrupt the function of DNA methyltransferases. DNMT inhibitors represent a promising class of epigenetic modulators as they can reactivate the expression of genes that have been repressed by DNA methylation and they exert antitumor and antiproliferative effects. These inhibitors are being investigated as potential drugs in cancer treatment, especially in combination with other therapies.