Small-cell carcinoma (SCC) of the esophagus is rare, and its clinical characteristics remain poorly understood. A 54-year-old man was given a diagnosis of esophageal SCC and underwent esophagectomy. Four months after surgery, he was admitted to our hospital because of rapidly developing hyponatremia. Syndrome of Inappropriate Secretion of Antidiuretic Hormone (SIADH) due to extensive recurrence of SCC was diagnosed. Combined chemotherapy with irinotecan and cisplatin has dramatically reduced metastatic tumors, and it was concomitantly effective for SIADH. This case demonstrates that esophageal SCC could induce SIADH as a paraneoplastic syndrome and that the above combined chemotherapy was feasible and effective.