A primary squamous cell carcinoma of the thyroid is extremely rare disease. We evaluated this disease by fine needle aspiration cytology in a 43 year-old female. On physical examination, the thyroid was moderately enlarged and palpated with hard consistency. The cytologic aspirate revealed nests of squamous cells, malignant squame and thyroid follicular cells in the necrotic background. We diagnosed this tumor as squamous cell carcinoma with cytologic evidence. Surgically resected thyroid revealed well differentiated squamous cell carcinoma. Immunohistochemical staining for antithyroglobulin proved that this tumor was primary in origin and clinical study confirmed this lesion to be of primary thyroid origin rather than metastasis or direct invasion from contiguous structures.