A child of 10 years 5 months presenting with chronic renal failure had bilateral cystic kidneys. Biopsy of a right lower-pole solid mass revealed nephroblastoma. At bilateral nephrectomy, both kidneys were both replaced by variable-sized cysts with a unifocal nephroblastoma on the right. Renal failure with nephroblastoma is uncommon and is usually either a manifestation of the Drash syndrome or a complication of chemotherapy. The need to assess both kidneys in a child with any other renal abnormality in addition to a renal mass should always be considered.