An 11-year-old female spayed Maltese presented comatose, half an hour after vehicular trauma, and was treated for traumatic brain injury and pulmonary contusions. The dog developed severe hypernatremia within six hours of presentation, which responded poorly to the administration of five percent dextrose in water. As central diabetes insipidus was suspected, desmopressin was trialled and resolution of hypernatremia was achieved six days later. Transient trauma-induced central diabetes insipidus has been described previously in two dogs; in the first, serum sodium concentrations were evaluated three days after injury and the other developed hypernatremia seven days after injury. To the authors’ knowledge, this is the first report of rapid onset, transient, and trauma-induced central diabetes insipidus in a dog that encompasses the complete clinical progression of the syndrome from shortly after injury through to resolution.