We describe a fatal case of adenovirus pneumonia accompanied by encephalitis in a neonate who showed lethargy on the 6th day and died on the 12th day. Adenoviral particles as well as viral intranuclear inclusions were noted in pulmonary alveolar epithelium cells. Neuropathological examination revealed diffuse oedema, perivascular cuffing and gliosis in the white matter. Adenovirus type 11 was isolated from lung, hilar lymph node, and brain tissue. This is the first instance of adenovirus isolation from brain tissue in a newborn infant. The virological and neuropathological findings suggest the invasion of neural tissue by adenovirus and substantiate the significance of neurological symptoms observed in neonatal adenovirus infection.