A case of Horner's syndrome is reported in a 8 month-infant after ultrasound guided, percutaneous internal jugular cannulation. This syndrome receded spontaneously after resolution of a laterocervical hematoma caused by reiterated venipunctures performed during the cannulation. Ultrasound imaging, by providing vizualization of the internal jugular vein and surrounding structures, may help to localize the vein and decrease the incidence of complications. Considering this case report and the cases previously reported in literature, the authors conclude that paediatric patients are at a higher risk compared to adults to develop Horner's syndrome following percutaneous internal jugular cannulation.