We report a rare case of diffusely infiltrative squamous cell carcinoma of the esophagus. The patient, a 68-year-old man, was admitted to our hospital for investigation of dysphagia. Esophagography and upper gastrointestinal endoscopy revealed esophageal stenosis and gastric cancer. As a biopsy from the esophagus revealed no sign of malignancy, he underwent only distal gastrectomy. After 3 months, the stenosis became worse. Again, biopsy from a gastrointestinal endoscopy showed no malignancy, but endobronchial ultrasound-guided transbronchial needle aspiration revealed squamous cell carcinoma of the esophagus. Despite various treatments, the patient died of disease progression 20 months after its onset. Autopsy revealed diffusely infiltrative squamous cell carcinoma of the esophagus, which is a rare malignancy with few case reports documented.