Polymorphous adenocarcinoma is a malignant salivary gland neoplasm that predominantly occurs in the minor salivary gland. Although 65% of the cases have a preferential localization in the palate, the tumor is also reported in the lip and buccal mucosa. The aim of this study is to report a case of polymorphous adenocarcinoma in a 69-year-old female patient who presented with an asymptomatic and normochromic nodule of unknown duration located in the left buccal mucosa, next to the parotid duct. An incisional biopsy was performed, and the microscopic analysis revealed proliferation of epithelial cells organized in solid and cribriform structures with perineural invasion. The final diagnosis of polymorphous adenocarcinoma was obtained. The patient was submitted to surgical treatment, and no recurrences were detected after 6 months of follow-up.