Vampire bat control strategies have not changed in México for more than 40 years. Anticoagulants and strychnine are frequently used to reduce bat populations and the prevalence of rabies. Despite these control efforts, vampire bat-borne rabies continues to have a significant economic impact. A new control method is being developed that takes advantage of the reproductive changes induced by phytoestrogens in mammals. In this study, we fed bats the phytoestrogen coumestrol, for 30 days and examined its effect on the reproductive organs of male and female vampire bats in laboratory tests. For males, coumestrol resulted in an increase in weight and loss of the typical histological structure of testes. Treated females had no corpora lutea in their ovaries and fewer primordial folliculi were observed. These results suggest that coumestrol might be a candidate replacement for anti-coagulants used for vampire bat control.