The symptoms, clinical signs, postmortem examination and histological findings of a rabbit with malignant thymoma are described. Moreover, the recent literature was reviewed with regard to symptoms, diagnosis, and treatment of thymoma in the rabbit. Malignant thymoma is a relatively rare tumour in rabbits. Symptoms are caused by the space-occupying mass in the cranial part of the thorax and include dyspnoea and inferior caval vein syndrome. Several paraneoplastic syndromes are associated with thymoma, of which bilateral exophthalmos is one of most striking in rabbits. A definitive diagnosis is difficult to establish antemortem. Surgical removal is the treatment of choice and has been succesfully performed in the rabbit. Little is known about the prognosis after surgery.