This report describes successful transspecies blood transfusion from a Magellanic horned owl (Bubo virginianus magellanicus) to a barn owl (Tyto alba). The barn owl was admitted to a wildlife rehabilitation center with severe anemia (packed cell volume [PCV] = 6.7%) from suspected anticoagulant rodenticide poisoning. Procedures performed included patient stabilization, pharmacological treatment, and persistent monitoring following the blood transfusion. The patient's PCV was measured daily, increasing progressively, and attaining a normal value for the species (PCV > 40%) on the eighth day posttransfusion. With no possibility of obtaining a same-species donor and because of the serious condition of the patient and unfavorable prognosis, a decision was made to perform the xenotransfusion. The result was a successful recovery and ultimately the release of the owl into its natural habitat. We concluded that xenotransfusion for avian species should be considered in cases with no possibility of obtaining a homologous donor.