Esophageal adenocarcinoma arising from ectopic gastric mucosa (EGM) is extremely rare. We describe here two Japanese patients with adenocarcinoma of the cervical esophagus arising from EGM. Case 1 is a 62-year-old man who had slightly red EGM in the cervical esophagus on upper gastrointestinal endoscopy (UGE). Because the biopsy showed atypical glands that were suspicious for adenocarcinoma, endoscopic submucosal dissection was performed. Histopathological examination revealed that the lesion was a well-differentiated adenocarcinoma (pT1a MM). Lymphovascular invasion was absent, and the margins were free from carcinoma. Case 2 is a 57-year-old man who had an elevated lesion with a bleeding tendency in an area of EGM in the cervical esophagus on UGE. Adenocarcinoma was diagnosed in the biopsy. Because of the presence of enlarged lymph nodes (#106recL), preoperative chemoradiotherapy was performed to reduce the size of the adenocarcinoma and lymph nodes prior to resection of the cervical esophagus and reconstruction with free jejunal grafts. Histopathological examination revealed moderately differentiated adenocarcinoma (0-I, pT2N1M0, pStage II). In both cases, adenocarcinoma was surrounded by EGM, which led to the diagnosis of EGM-derived esophageal adenocarcinoma. Here, we report its immunohistochemical characteristics in the present cases and discuss the histogenesis.