A 28-year-old man with Gardner syndrome was admitted to our Department because of multiple abdominal masses. Abdominal computed tomography revealed severe hydronephrosis of both kidneys due to ureteral compression against the pelvic bones exerted by multiple solid abdominal masses. The patient developed oligoanuria. Right percutaneous nephrostomy tube placement was followed by restoration of diuresis and progressive recovery of renal function of the left side. The patient then underwent median laparotomy and removal of five large desmoid tumors originating from the abdominal wall. Bilateral ureteral obstruction due to abdominal desmoid tumors can be a rare urologic complication of Gardner syndrome.