A case of Warthin's tumor of the parotid gland which extensively extended into the parapharyngeal space is presented. The tumor border against the parotid gland was ill-defined but the border towards the parapharyngeal structures was clear. Solid portions of the tumor appeared hypointense relative to the gland on both unenhanced T1- and T2-weighted MR images without fat suppression, whereas cystic portions appeared hypointense on T2-weighted images and hyperintense on unenhanced T1-weighted images. Pathologic study showed that the ill-defined margin was caused by inflammation and cystic material consisted of highly proteinaceous material. We concluded that the atypical extension into the parapharyngeal space of the tumor was caused by its location in the deep lobe of the parotid gland and its bulky size.