Increased risk of gastric cancer has been reported in patients with chronic atrophic gastritis that develops in conjunction with pernicious anemia. We report here a case of a gastric adenocarcinoma associated with pernicious anemia. A 40-year-old female patient had been diagnosed with anemia 6 years earlier at a local hospital. One month ago, she visited our hospital for aggravated dizziness and newly developed epigastric soreness. Her blood hemoglobin level was 4.2 g/dl, and a gastroscopic work-up for anemia discovered a 2.5-cm-sized, slightly elevated mucosal lesion at the anterior wall of the high body in the stomach. The biopsy of this lesion revealed a moderately-differentiated adenocarcinoma. She underwent a total gastrectomy with a Roux en Y esophagojejunostomy with D2 lymph node dissection. The final stage of the gastric carcinoma was identified as T1N0M0. Based on this experience, we recommend that a follow-up gastroscopy be performed in patients with pernicious anemia with atrophic gastritis because of the increased risk of gastric cancer in patients with pernicious anemia.