Salivary duct carcinoma is a high-grade malignant tumor arising predominantly in the major salivary glands. We describe herein a rare presentation of salivary duct carcinoma arising in the submandibular gland and showing pagetoid spread to the oral mucosa. A 46-year-old man was admitted with a 2-year history of swelling in the floor of the mouth. Resection of the submandibular gland tumor was followed by mucosal biopsy around the aperture of the right Wharton's duct. The tumor recurred in the oral mucosa with pagetoid spread and extended widely in the oral cavity for the following 10 years, despite chemo- and radiotherapy. Mucosal spread, although a relatively remote possibility, can occur in the setting of salivary duct carcinoma.