Horner syndrome or oculosympathetic paresis is a neurological pathology that occurs when the hypothalamus originating from the oculosympathetic nerve pathway is interrupted at any point from the hypothalamus to the end. The disease is clinically characterized by myosis, ptosis, endophthalmitis, and anhidrosis of the face. Iatrogenic Horner syndrome due to tube thoracostomy is very rare. Tube thoracostomy is a commonly used surgical procedure in different pulmonary pathologies. However, various risks may arise depending on the techniques used during the insertion of the tube, the placement of the tube in the thorax, and the length of time the tube remains in the thorax. In this paper, a case of ptosis on the second day of hospitalization due to tube thoracostomy for spontaneous pneumothorax was presented and discussed.