We report an autopsy case of encephalitis principally confined to the bilateral thalamus and associated with pulmonary and gastric cancers. An 81-year-old man exhibiting behavioral abnormalities and progressive somnolence died of pneumonia 11 months after onset. Because the patient had lung cancer and no definite cause of the encephalitis was found, this case was categorized as one of paraneoplastic encephalomyelitis. This may be the first reported case of this condition in which the central nervous system (CNS) lesion was located predominantly in the thalamus.