Ipsilateral tonsillectomy and panendoscopy-guided biopsy following imaging studies are considered a standard procedure in the search for a primary origin in patients with cervical metastatic carcinoma of unknown origin(MUO). However, many authors recommended bilateral tonsillectomy for the determination of the primary site of a MUO, because cervical metastasis may occur contralateral to tonsillar carcinoma. The authors attempted to address the clinical implications of using routine bilateral tonsillectomy to determine the primary site of MUOs based on a case report of cervical MUO that was finally diagnosed as a bilateral synchronous tonsillar carcinoma with cervical metastasis after a diagnostic work-up that included bilateral tonsillectomy.