Symptomatic diffuse idiopathic skeletal hyperostosis (DISH) is not common. Gelfoam is one of the most commonly used topical hemostatic agents. But, in the partially moistened state, air retained in its pores may result in excessive expansion on contact with liquid. The onset of swallowing difficulty after anterior cervical spine surgery due to appling gelfoam is a rare complication. A 77-year-old man with swallowing difficulty was admitted to our hospital and we diagnosed him as DISH confirmed by radiological study. After removing the DISH, patient's symptom was relieved gradually. However, on postoperative day (POD) 7, the symptom recurred but lesser than the preoperative state. We confirmed no hematoma and esophageal perforation on the operation site. We observed him closely and controlled the diet. Three months later, he had no symptom of swallowing difficulty, and was able to be back on a regular diet, including solid foods. We present a complication case of swallowing difficulty occurring by gelfoam application.