A new-born (8-day-old) male marmoset (Callithrix jacchus) was found dead in a zoo. The littermate and parents had no clinical abnormalities. By gross observations at necropsy, there were moderate to severe multiple necrotic foci in the liver and heart. Histopathological examinations also revealed mild focal necrosis with neutrophilic infiltration in the cerebral cortex. By Giemsa stained sections, intracytoplasmic bundles of large bacilli were observed in the hepatocytes, intestinal epithelial cells, cardiac myocytes and neuronal cells around the necrotic lesions. Immunohistochemically, these bacilli were intensely positive for rabbit sera against Clostridium piliforme, RT and MSK strains. Although Tyzzer's disease has been rarely reported in primates, the central nervous system (CNS) lesions by Clostridium piliforme infections are very unusual.