Basaloid squamous cell carcinoma （BSCC） is a rare variation of squamous cell carcinoma which was first described by Wain in 1986. According to the WHO classification, BSCC shows high malignancy and poor prognosis. Alcohol consumption and smoking are thought to be associated with the onset of this tumor. We report a case of BSCC at the floor of the mouth in a 62-year-old man. Physical examination demonstrated a 25×20mm mass at the left floor of the mouth. Histological examination revealed that the tumor consisted of solid nests of basaloid cells, comedo-like necrosis within tumor islands, cellular pleomorphism and nuclear mitotic activity, and epithelial dysplasia adjacent to the tumor. A pathological diagnosis of BSCC was made. The patient underwent wide resection of the oral floor tumor with marginal left mandibulectomy and functional neck dissection of the left side. Two years later, the patient remains in good health and free of disease.