Dexmedetomidine, an alpha(2)-adrenergic agonist, decreases lipolysis and thus prevents nonshivering thermogenesis in infants. We report the case of a two-day-old neonate who received dexmedetomidine for sedation and analgesia after undergoing primary repair of bladder exstrophy. After 9 hours, the patient developed bradycardia and profound hypothermia. The bradycardia was unresponsive to anticholinergics but resolved approximately two hours after radiant heat was applied. This report highlights the potential profound impact of dexmedetomidine on thermoregulation in neonates. Dexmedetomidine impacts thermoregulation in neonates and its use warrants careful attention to the control of temperature and to the routine use of exogenous heat.