Thymic carcinoid is an extremely rare malignancy. This tumor is often associated with endocrine disorders such as Cushing's syndrome, multiple endocrine neoplasia type 1 and superior vena cava syndrome. We describe the case of a 44-year-old Italian woman with metastatic atypical thymic carcinoid secreting ectopic adrenocorticotropic hormone who was treated with adaptive radiation therapy with a curative dose schedule for a symptomatic mediastinal tumor. After 22 months, the patient was in good clinical condition, presenting stable disease without any evidence of local or systemic progression. To our knowledge there are no previously reported data regarding radical radiotherapy in the treatment of thymic carcinoids.