Iatrogenic Horner’s syndrome is a rare complication that can occur after trauma, cervical central line insertion, chest tube insertion, and rarely following adult thoracic and neck surgery, especially in high risk patients with hypertension and diabetes. The majority of cases reported in the literature describe non-iatrogenic Horner’s syndrome in adults as an unusual presentation for cervical tumours or apical lung carcinoma. In children, there are some reports describing acquired Horner’s syndrome following trauma or invasive intervention near the cervical–thoracic area. Less has been written about the incidence of Horner’s syndrome following paediatric cardiac surgery.