Thymic carcinoid tumors very rarely occur during childhood and are often associated with the production of adrenocorticotropic hormone (ACTH), which leads to Cushing’s syndrome. We describe a 7-year-old male patient with a thymic atypical carcinoid tumor who presented with cyclical Cushing’s syndrome. His tumor was initially overlooked on computed tomography scanning in the anterior mediastinum, and was later identified by magnetic resonance imaging scanning. There was an interval of 154 days observed between periods of cyclic hormone production. In addition, we discuss the findings of our literature search of the PubMed database. This report emphasizes the importance of considering thymic carcinoid in the differential diagnosis of ectopic ACTH production in children.