A 68-year-old man with a history of nephrectomy of the right kidney was admitted to our hospital with a 1-month history of polyuria (> 41 per day). He also exhibited hyposthenuria, which was unresponsive to treatment with exogenous vasopressin. Radiographic examination revealed partial obstruction of the left ureter and moderate hydronephrosis. The cause of the obstruction was cancer of the ureter. After drainage using a nephrostomy tube, the polyuria and hyposthenuria were gradually resolved. This is the first known case of nephrogenic diabetes insipidus due to hydronephrosis in a patient with a solitary kidney.