Myelodysplastic syndromes (MDS) are clonal bone marrow malignancies characterized by peripheral cytopenias and dysplastic changes in the bone marrow with various clinical features. Patients with MDS, in particular those with intermediate-2 (Int-2) and high-risk disease, have a poor prognosis. The mainstay of treatment includes cytoxic chemotherapy and supportive care. Over the last decade, promising results from studies focusing on hypomethylating agents, such as decitabine (5-aza-deoxycytidine) and 5-azacitidine, have led to the expansion of the therapeutic arsenal for MDS. This review presents the current data available on the clinical efficacy and safety profile for decitabine as a treatment for MDS. Although not fully understood, decitabine's antitumor activity may involve its ability to induce hypomethylation and reactivation of genes responsible for cellular differentiation, stimulate an immune response, induce DNA damage/apoptotic response pathways, and/or augment stem cell renewal. Future studies that use epigenetic therapies that combine hypomethylating agents with histone deacetylase inhibitors (HDACi) and head-to-head comparison studies of decitabine and 5-azacitidine will provide valuable pre-clinical and clinical data, enhancing our understanding of these drugs.