Polymorphous adenocarcinoma (PAC) is a distinctive salivary gland neoplasm that predominantly occurs in the minor salivary glands. The tumor is characterized by cytological uniformity, morphological diversity, an infiltrative growth pattern and low metastatic potential. It presents as an asymptomatic, slow- growing mass within the oral cavity. This salivary gland tumor is difficult to diagnose both clinically and histopathologically due to its indolent presentation and diverse architectural pattern which includes various microscopic patterns namely- solid, ductal-tubular, cribriform, trabecular and single-file growth. Hence, Immunohistochemistry plays a very important role in diagnosing this tumor. We hereby report a rare case of PAC occurring in a 50yr old female patient presenting with a lesion in right upper posterior part of alveolus extending to the hard palate.