A 4-year-old Java sparrow (Lonchura oryzivora) was diagnosed with thymic lymphoma based on the results of histopathologic evaluation and immunohistochemical staining of a Tru-cut biopsy sample. The bird was treated with chlorambucil (2 mg/kg PO) twice per week for the first 18 weeks, and the mass size, activity level, appetite, bowel function, and body weight were monitored weekly. At week 19, the bird became ill and anorexic, and the chlorambucil treatment was discontinued. The neoplasm grew rapidly during weeks 20 and 21, and the chlorambucil treatment was resumed at week 23. At week 28, the bird's overall condition worsened and the chlorambucil treatment was discontinued because no additional reduction in mass size had occurred. At week 29, prednisolone (2.2 mg/kg) was administered orally every 12 h for 31 weeks. At week 61, the patient became acutely ill, exhibiting anorexia and a decreased level of physical activity, and the owner elected to euthanatize the bird. This is the first report of long-term management of thymic lymphoma in a Java sparrow.