Viral vectors have been frequently used as vaccine-delivery vehicles. Both DNA and RNA viruses have been employed for vaccine development. Viral vectors based on adenoviruses (Ad), adeno-associated viruses (AAV), herpes simplex viruses (HSV), lentiviruses (LV), alphaviruses, flaviviruses, measles viruses (MV), rhabdoviruses, Newcastle disease virus (NDV), poxviruses and picornaviruses have been utilized. Approaches have included the expression of tumor-associated antigens and immunostimulatory genes as well as administration of oncolytic viruses. Prophylactic and therapeutic proof-of-concept has been established in preclinical animal tumor models, and therapeutic efficacy has been obtained in clinical trials in human cancer patients. Model viral vector systems and their applications in cancer vaccine development are described here.