A 73-year-old Japanese man with Hashimoto's disease and diabetes mellitus received regular medical checkups for type 2 diabetes care. Blood tests indicated macrocytic anemia (red blood cell count, 279×104 /μL; hemoglobin, 12.2 g/dL; hematocrit, 34.0%; mean corpuscular volume, 121.9 fL). The laboratory data demonstrated a normal folic acid level with a low vitamin B12 level. An endoscopic examination indicated no signs of gastric or intestinal bleeding. Positive results for anti-intrinsic factor antibodies were strongly suggestive of pernicious anemia. The patient refused cobalamin injections to treat the anemia. However, the oral administration of mecobalamin for the treatment of diabetic neuropathy was simultaneously initiated. Subsequently, the anemia gradually improved. Oral mecobalamin was presumably effective for pernicious anemia management. Anemia is frequently observed in elderly patients, and the incidence of pernicious anemia increases with age. Anemia is conventionally treated with cobalamin injections. Currently, the oral administration of mecobalamin is not the typical treatment for anemia. However, as in our case, a few reports have documented positive results following oral mecobalamin treatment. Moreover, oral mecobalamin is a fairly recent, novel, noninvasive mode of treatment, making it ideal for elderly patients, who are generally frail. This case suggests the efficacy of mecobalamin for the treatment of pernicious anemia.