Pernicious anemia is the frequent cause of megaloblastic anemia, and it is the result of a vitamin B12 deficiency due to the decrease or absence of intrinsic factor (IF) because of gastric mucosa atrophy or autoimmune destruction of IF-producing parietal cells. With the existence of a severe gastric atrophy, there is a decreased in acid and IF production and a further change in vitamin B12 absorption. Mercury is ubiquitous in nature and exists in 3 forms, elemental mercury, inorganic salts and organic compounds. Organic forms, specifically methyl mercury, are the most toxic of the 3 classes of mercurials. Methyl mercury exerts its most devastating effect on the central nervous system by causing psychiatric disturbances, ataxia, visual loss, hearing loss, and neuropathy. We report a case of mercury intoxication associated with pernicious anemia. The 77 years old patient was referred to Yeungnam University Hospital for tongue pain, somatitis, headache and aggressive behavior. He had taken an unevaluated medicine for a long time. After clinical evaluation, this case was diagnosed as a pernicious anemia and the unevaluated medicine was made up of mercury. After the administration of D-penicillamine and intramuscular injection of BAL and cobalamine, clinical symptoms and aggressive behavior were improved as well as laboratory findings.