Horner's syndrome is characterized by a combination of ipsilateral miosis, blepharoptosis, enophthalmos, facial anhidrosis, and iris heterochromia in existence of congenital lesions. The syndrome results from a disruption of the ipsilateral sympathetic innervation of the eye and ocular adnexa at different levels. Though rare, thyroid and neck surgery could be considered as possible causes of this clinical entity. We present a case of Horner's syndrome in a patient after total thyroidectomy and neck dissection for medullary thyroid cancer with neck nodal disease and attempt a brief review of the relevant literature.