A multicentric squamous cell carcinoma was found in the oral cavity of an adult female Franc ois's leaf-monkey (Trachypithecus francoisi francoisi). The monkey showed apparent swelling of the facial region, and physical examinations revealed gingival swelling and osteolysis of both the mandible and maxillary region. Incisor regions of the maxillary and mandibular bones were replaced by neoplastic tissue, and a white nodule was found on the right cervical lymph node. Histopathological examinations revealed that the neoplasm was composed of multiple variably-sized islands of malignant neoplastic squamous epithelial cells with metastasis to the right cervical lymph node. This is the first report of oral squamous cell carcinoma in a leaf-monkey reared at a Japanese zoo.