Successful xenotransfusion in an island fox (Urocyon littoralis clementae) has not been previously reported but may be necessary in an emergency. An 11-yr-old male, intact, captive island fox was exhibiting clinical signs of rattlesnake envenomation including hypoperfusion, tachypnea, facial edema, and multifocal facial and cervical ecchymosis. Blood work revealed severe thrombocytopenia (18 K/μl) and anemia (Hct 15.8%). A presumptive diagnosis of rattlesnake (Crotalus sp.) envenomation was made. Initial treatment included oxygen therapy, fluid therapy, antibiotics, antacids, pain medications, and polyvalent crotalid anti-venom. Emergency xenotransfusion using whole blood (45 ml) from a domestic dog was used due to worsening clinical signs from anemia. No acute or delayed transfusion reactions were observed in the fox and the patient made a full recovery 5 days later. Successful xenotransfusion in an island fox using whole blood from a domestic dog (Canis lupus familiaris) is possible and may be lifesaving.