We report a 6-month-old boy with abdominal aortic aneurysm and dysplastic kidneys. To the best of our knowledge, this is the first report of abdominal aortic aneurysm associated with dysplastic kidneys. Serial US, MR angiography and scintigraphy were performed. No underlying cause of the aneurysm was identified. Spontaneous thrombosis occurred within 2.5 years of diagnosis, but there was persistent renovascular hypertension and progressive deterioration of renal function.