We report the smallest case of the balloon aortic valvuloplasty via a carotid artery. A baby boy weighing 890 g suffered from a severe aortic stenosis. Balloon aortic valvuloplasty using a TMP-Ped 4-mm balloon catheter succeeded in resolving severe aortic stenosis without any complications. Balloon aortic valvuloplasty via a carotid artery can be a first-line treatment even for extremely-low-birth-weight infants.