Dysphagia is a symptom of head and neck cancer itself and a significant complication of its treatments. Radiation therapy also causes dysphagia due to radiation toxicity. Therefore, it is necessary to evaluate patients who complain of dysphagia after radiation therapy. A video fluoroscopic swallowing study (VFSS) is an imaging tool that can diagnose dysphagia objectively from the oral to the esophagus phase. This tool is also used to evaluate to radiation-induced dysphagia. The abnormal findings in each swallowing phase are diverse. Interpreting each abnormal finding in relation to periodic complications caused by radiation toxicity is very important. A delayed pharyngeal transit time is the most characteristic abnormal finding of VFSS due to fibrosis, which is a chronic complication. To accurately assess the radiation-induced dysphagia, an evaluation of dysphagia prior to radiation therapy in head and neck cancer patients should be preceded. A multidisciplinary approach for evaluating dysphagia is needed throughout the entire period of head and neck cancer treatment.