Mesenchymal stem cells (MSCs) from post-natal bone marrow possess tremendous potential for cell-mediated gene therapy in several disease processes, and recent reports have broadened the spectrum for therapeutic applications to cancer therapy. The evidence that sites of active tumorigenesis favor the homing of exogenous MSCs have support the rationale for developing engineered MSCs as a tool to track malignant tissues and deliver anticancer agents within the tumor microenvironment. Several reports have proven the efficiency of MSCs as cell carrier for in vivo delivery of various clinically relevant anticancer factors, including cytokines, interferon, pro-drugs or replicative adenovirus, and tumor growth inhibition following engraftment within or in the vicinity of tumor. The enthusiasm for MSCs is further reinforced by the striking observation that unmodified MSCs can exert antitumorigenic activity, and preliminary reports in immunocompetent animals have provided encouraging results for the use of MSCs in cancer immunotherapy. This review highlights recent works and potential clinical applications of MSCs in this field.