A young male presented within hours after closed head injury with hypotension, tachycardia, and polyuria. A diagnosis of post-traumatic diabetes insipidus was made. Although a rare entity, the rapid diagnosis of diabetes insipidus and early treatment with vasopressin may have been life-saving in this case. A detailed approach for treatment with continuous intravenous vasopressin may be the most accurate and efficient method of managing acute onset diabetes insipidus, especially in the hemodynamically compromised patient. This will allow for a controlled fluid management in order to achieve hemodynamic stability and prevent aggravation of cerebral edema.