Reoviruses are nonenveloped, segmented, double-stranded RNA viruses capable of infecting a wide range of invertebrate, vertebrate, fungus, and plant hosts. Though sporadic infection has been reported in a variety of reptilian species, infection of rough green snakes (Opheodrys aestivus) has not been previously described. Five wild-caught, adult rough green snakes were obtained by a zoological institution. Clinical deterioration was first noted in all snakes after 3 weeks in quarantine. Despite treatment, clinical decline progressed, and all 5 snakes died or were euthanized by 48 days post-arrival. Moderate, multifocal, acute, necrotizing hepatitis with hepatocellular syncytia was diagnosed in 1 snake. Two additional snakes had severe, diffuse, subacute to chronic pancreatitis. All 5 snakes had gastroenteric cryptosporidiosis. Electron microscopic examination of liver from the snake with hepatic lesions revealed scattered hepatocytes containing 1 or more intranuclear clusters of approximately 90 nm in diameter viral particles arranged in loose arrays. Polymerase chain reaction (PCR) amplification of a segment of the reovirus RNA-dependent RNA polymerase gene was performed on RNA extracted from tissues of all 5 snakes. PCR amplification of samples extracted from the snake with hepatic lesions resulted in a 109-base pair (bp) product. Phylogenetic analyses indicated the virus was a novel strain distinct from other reoviruses at a level consistent with species difference. The source of infection was unknown. PCR amplification of samples extracted from the other 4 snakes was negative.