The subcutaneous cervicofacial emphysema is a rare and serious disease. There is a wide variety of etiologic factors for subcutaneous cervicofacial emphysema. As an maitrisable factor, the use of hydrogen peroxide 3% as an irrigant to newly operated tissue plans may cause emphysema. We report here a case with iatrojenic cervicofacial emphysema, occurred after the irrigation of hydrogen peroxide 3% to the drilled teeth root during dental treatment.