Ferlaviruses have been associated with significant mortality events in squamates. Over a 5-month period in 2012, a mortality event at the Phoenix Zoo involved seven rattlesnakes (Crotalus spp.), a Sonoran gopher snake (Pituophis catenifer affinis), and a Gila monster (Heloderma suspectum). All individuals had been managed within the same group of enclosures at the zoo, and many of the affected individuals had previously been housed together. Clinical signs during the outbreak included sudden death, agonal behavior, anorexia, regurgitation, and loss of body condition. Histologic findings were similar in all animals, with lesions primarily in the respiratory tract and pancreas; these findings were consistent with viral infection, and in five of the seven cases for which samples were submitted, RT-PCR identified a genogroup C Ferlavirus. The findings in this outbreak support the possibility of cross-species viral transmission and clinical disease associated with genogroup C Ferlavirus infection and suggest persistence of paramyxoviral infection within captive reptile populations. These findings have widespread implications for the management of mixed reptile species habitats in zoological and private collections, and suggest a need to include all reptiles, not just snakes, in preshipment and quarantine investigation of potential ferlavirus infection.