Propranolol has been the new standard-of-care treatment for infantile hepatic hemangioma (IHH) cases necessitating medical treatment based on a case series in 2008 that reported how propranolol resulted in involution of cutaneous infantile hemangioma in 2 patients with heart failure. The mechanism of action of propranolol on cutaneous infantile hemangiomas and IHHs is not well-understood, although new research suggests that hemangiomas and other vascular tumors express high amounts of β1 to β3 receptors, and thus explains why these vascular tumors are susceptible to beta-antagonists. However, there are reports of adverse side effects with the use of propranolol, including hypoglycemia, bronchial hyperreactivity, and sleep disturbances. There has been an interest in utilizing selective beta-antagonists to avoid potential side effects of propranolol in treating vascular tumors. We report the first documented case of a 4-month-old patient with diffuse IHH successfully treated with atenolol.