Mixed squamous cell carcinoma and papillary carcinoma in the thyroid gland is a very rare malignant tumor characterized by rapidly progressive clinical course and radioresistance. A 63-year-old woman had mixed squamous cell carcinoma and papillary carcinoma in the thyroid gland diagnosed by fine needle aspiration cytology (FNA), and the diagnosis was confirmed by histological examination. She had complained of a fixed, egg-sized mass of the anterior neck with hoarseness for 1 year. The findings of FNA consisted of sheets and clusters of polygonal epithelial cells with hyperchromatic, pleomorphic nuclei and eosinophilic, abundant, laminated cytoplasm. These findings were consistent with squamous cell carcinoma. Also, fool of papillary carcinoma were noted, and the cells exhibited nuclear groovings and intranuclear cytoplasmic inclusions. Total thyroidectomy specimen showed a diffusely infiltrating tumor in the left thyroid which was composed of mixed papillary carcinoma and well-differentiated squamous cell carcinoma. In junction between two components, squamous metaplasia of papillary carcinoma was noted.