Diffuse idiopathic skeletal hyperostosis (DISH) is a common disease in which ossification lesions occur in the bones including the vertebrae. Dysphagia may occur in advanced cases, but there are few cases that require treatment. A 68-year-old man was diagnosed with hypopharyngeal cancer of the left pyriform sinus and asymptomatic DISH on the anterior cervical vertebrae. Due to prior history of radiation, partial laryngopharyngectomy was performed. After surgery, severe dysphagia and aspiration pneumonia occurred, and the patient needed to undergo total laryngectomy. It was determined that dysphagia was due to multiple factors, including insufficient laryngeal elevation and esophageal compression by osteophytes of DISH. Asymptomatic DISH can cause severe dysphagia after partial laryngopharyngectomy. We suggest that evaluation of the swallowing function and surgical options, including laryngeal suspension and cricopharyngeal myotomy should be considered when performing partial laryngopharyngectomy in patients with DISH, even if they demonstrated no difficulties in swallowing before treatment.