The occurrence of a mixed tumor containing papillary thyroid carcinoma (PTC) and primary squamous-cell carcinoma (SCC) is rare because there is no squamous epithelium in the thyroid gland. Reported herein is a 30-year-old female with mixed PTC and primary sec of the thyroid presented as thyroid incidentaloma. Fine-needle aspiration biopsy of the thyroid nodule revealed the presence of malignant thyroid cells. The histopathological examination following total thyroidectomy yielded two mixed, morphologically distinct histotypes that included PTC and sec. After total thyroidectomy, the patient underwent radioactive iodine therapy. No recurrence or metastasis occurred during the 20-month follow-up period after the operation.