We report the first case of retroperitoneoscopic ureterocalicostomy in a 17-year-old male patient with severe left hydronephrosis caused by a long congenital upper ureteral stenosis. With a retroperitoneoscopic approach, the stenotic segment was resected, the thin renal parenchyma overlying the lower calyx was fenestrated by a modest excision, and the proximal ureter was anastomosed to the lower pole in an end-to-end manner. At 2 years postoperatively, the patient was asymptomatic, with a significant reduction in hydronephrosis and a patent upper ureter. Retroperitoneoscopic ureterocalicostomy is technically feasible and can provide long-term successful reconstruction of a complicated ureteropelvic junction obstruction.