A 49-year-old female scarlet macaw ( Ara macao ) was presented with a mass in the cervical region. The bird showed no evidence of pain or discomfort, it swallowed food normally, and its breathing pattern was unremarkable. Results of contrast radiographic imaging revealed a well-demarcated mass in the right cervical region not related to the crop. After surgical resection and histopathologic evaluation, a malignant nodular stage of an epithelioid cortical-type thymoma was diagnosed. One year later, metastasis of the thymoma to the lung was diagnosed and confirmed at postmortem examination. The final diagnosis was corrected to malignant nodular stage of an epithelioid cortical-type thymoma with metastasis to the lung. This is the first report in an avian species of a malignant thymoma with metastasis to the lung after complete resection of the initial cervical thymoma and a survival time of 1 year.