Objective To describe a case of inappropriate antidiuretic hormone (ADH) secretion in a dog secondary to trauma. Case Summary A 14‐year‐old neutered female mixed breed dog presented for evaluation of bite wounds. The dog sustained multiple puncture wounds to the cervical area, stifle, and elbow. Treatment was initiated with isotonic crystalloid fluids, analgesia, broad‐spectrum antimicrobials, and gastroprotectants. The dog developed hyponatremia with concurrent serum hypoosmolality and inappropriate urine hyperosmolality and urine sodium secretion, leading to a diagnosis of the syndrome of inappropriate ADH secretion. The hyponatremia improved, and the dog improved clinically and was discharged 3 days after admission. New or Unique Information Provided This is the first case description of the syndrome of inappropriate ADH secretion in a dog suffering from trauma. Inappropriate ADH secretion is largely under‐recognized in veterinary patients. Increased awareness of this syndrome can lead to initiation of appropriate treatment and improved outcomes.