Developmental anomalies of inferior vena cava are a rare cause of ureteral obstruction. We report a case that presented with right upper ureteral obstruction that radiologically simulated a retrocaval ureter. An aberrant vessel, which caused obstruction of the right ureter was identified at operation and surgical relief of ureteral obstruction was performed. Inferior venocavography was performed postoperatively and disclosed an unusual incomplete duplication of inferior vena cava. Our findings suggested that ureteral obstruction by incompletely duplicated anomaly of the inferior vena cava should be included in the differential diagnosis of extrinsic ureteral obstruction.