Adenosquamous cell carcinoma of tonsil is a rare lesion of head and neck and is often misdiagnosed as squamous cell carcinoma. It has a very aggressive clinical pattern. We encountered a patient with an adenosquamous cell carcinoma of tonsil and performed various treatment modalities including surgical resection, radiation therapy, chemotherapy but the patient expired two years after the first diagnosis. Such case has never been reported earlier in Korea. Herein, we present this rare case with a review of related literature.