Abstract: Oncolytic adenoviruses have been used in cancer gene therapy because of their ability to selectively transfect and replicate in tumor cells. However, systemically administering oncolytic adenoviruses is often inefficient because the host's immunity also attacks the viruses. Delivering oncolytic adenoviruses by loading them into mesenchymal stem cells effectively solves this problem. Mesenchymal stem cells have been described to possess a tumor-homing ability, as well as the capacity to deliver oncolytic adenoviruses. This review discusses the current challenges faced by oncolytic adenovirus delivery via mesenchymal stem cells.