Here, we report on four cases of gastric cancer in patients with autoimmune gastritis (AIG). AIG is characterized by the corpus-predominant atrophic gastritis with preserved antrum caused by autoimmune mechanisms. Although AIG is a high risk factor for gastric cancer and neuroendocrine tumors (NET), there are few reports describing the characteristics of gastric cancer in patients with AIG. In this case report, all four cases were diagnosed as having AIG by endoscopic findings and the presence of extra-gastric autoimmune diseases before the treatment for gastric cancer