Abstract: Background and Objectives: Avian parthenogenesis is embryonic development that occurs without fertilization. Virgin birds exhibiting parthenogenesis have reduced reproductive performance following mating. Previously in the 1960s, in vivo exposure of chickens and turkeys to certain live viruses was shown to increase the incidence of parthenogenesis as well as parthenogen size. However, no modern information is available on the effect of current virus vaccine strains or their mode of action on parthenogenesis in poultry. Hence, the objectives of this study were to determine the in vivo and in vitro effects of live pigeon pox (PP) virus as well as the in vitro effect of live Newcastle disease (ND) virus on parthenogenesis. Materials and Methods: Two experiments were conducted using virgin Chinese painted quail hens. The in vivo effect of live PP virus following vaccination and the in vitro effects of live PP and ND viruses following direct administration over the germinal disc of cultured quail eggs on parthenogenesis were determined. Results: It appears that vaccination of virgin hens with live PP virus has the potential to increase parthenogenesis as well as parthenogen size by the direct action of the virus on the embryo. Moreover, under in vitro conditions, live ND virus was found to exert similar effects as live PP virus. Conclusion: As vaccination for pox and ND is a routine practice in the modern poultry industry, it is possible that vaccination of birds carrying the parthenogenetic trait could impact their overall fertility and hatchability.