Although intramural spreading from gastric carcinoma to the esophageal wall is occasionally reported, longitudinal intramural lesion of the esophagus is very rare. We herein report the case of a patient found to have a carcinoma of the gastric cardia with intramural spreading to the esophagus approximately 7.0 cm in length. A 65-year-old man was admitted to our department suffering from a persistent midthoracic pain and mild dysphagia during the previous 3 months. Upper gastrointestinal studies revealed an oval submucosal tumor of the lower esophagus and a flare irregular lesion on the esophagogastric junction. An endoscopic ultrasonography showed the main tumor was in the submucosal layer and invaded beyond the muscularis propria. Histopathological examination of the resected specimen confirmed a poorly differentiated adenocarcinoma, 7.0 cm in length, which penetrated through the gastric wall, and invaded the submucosal layer of the esophagus. When only a few scattered carcinoma cells infiltrate only the mucosa or submucosa, it is difficult to diagnose the extent of esophageal invasion. In treating patients with gastric cancer with esophageal invasion, it is important to determine the safety of the proximal margin for esophageal resection. Histological examination using frozen sections obtained during surgery is essential for deciding the operative safety margin.