A 15-yr-old, male, captive red-tailed boa (Boa constrictor constrictor) was submitted for postmortem examination after it was euthanized after becoming nonresponsive and laterally recumbent. The snake had a history of respiratory disease, coelomic swelling, leukocyte intracytoplasmic inclusion bodies, and an antemortem negative Reptarenavirus PCR. At necropsy, there were solid white masses in the lungs and throughout the alimentary tract, and firm, smooth yellow masses in the pericardium and adventitia of heart base vessels. Histopathology revealed an anaplastic large-cell lymphoma that infiltrated multiple tissue types, most severely the lungs and esophagus. Neoplastic lymphocytes were negative for CD3 and positive for Pax5, consistent with a B-cell lymphoma. The yellow pericardial masses were composed of neoplastic neuroendocrine cells with moderate amounts of vacuolated cytoplasm and small, ovoid nuclei with finely stippled chromatin arranged in packets separated by fine fibrovascular stroma. Neoplastic cells were positive for β-endorphin consistent with a diagnosis of paraganglioma. Additionally, many cell types, including neoplastic lymphocytes and neuroendocrine cells, contained cytoplasmic viral eosinophilic inclusions, and Reptarenavirus PCR on spleen detected a virus in the species Reptarenavirus giessenae. This snake was diagnosed with concurrent paraganglioma, inclusion body disease, and anaplastic lymphoma, morphologically represented as a diffuse lymphoma of B-cell phenotype. Whether Reptarenavirus predisposes to neoplasia in snakes is debated. This case describes multiple neoplasms in a snake with a concurrent Reptarenavirus infection.