BackgroundHorner’s syndrome is a very rare complication following surgery of the thyroid gland with only a handful of cases reported in the literature. Exact pathophysiology of post-thyroidectomy Horner’s syndrome is not fully understood, and once diagnosed, management remains mostly conservative.Case presentationA 36-year-old Sri Lankan Sinhalese woman developed unilateral partial ptosis with enophthalmos and myosis one week after total thyroidectomy for a benign multinodular goiter. A clinical diagnosis of Horner’s syndrome was made. A postoperative ultrasound scan did not show a collection or hematoma compressing the sympathetic trunk. Our patient was managed conservatively and she had a slow and an incomplete recovery at 1-year follow up.ConclusionsThis case report highlights the importance of being aware of the close anatomical relationship between the thyroid gland and cervical sympathetic trunk during thyroidectomy. This would enable the surgeon to undertake measures to minimize the risk of damaging the sympathetic trunk during thyroidectomy.