Thymic carcinoids are classified into three categories: (1) nonsecretory tumors, (2) hormonal secretory tumors, and (3) tumors associated with multiple endocrine neoplasia type 1. We report a rare case with adrenocorticotropic hormone secreting thymic carcinoid with multiple endocrine neoplasia type 1. Radiologic examination showed an anterior mediastinal mass and a parathyroid tumor. Blood analysis revealed high levels of parathyroid hormone and adrenocorticotropic hormone. Urine cortisol and 17-hydroxycorticoids levels were also elevated. Extended thymectomy was performed. Subsequently adjuvant radiation therapy and parathyroid tumor resection were performed. A germline mutation of exon 7 in the multiple endocrine neoplasia type 1 gene was detected and a somatic mutation of exon 9 was demonstrated in the thymic tumor.