A captive male Bolivian squirrel monkey (Saimiri boliviensis) of less than 1 year of age died following diarrhea and debilitation on the day of death. At necropsy, necrotizing enteritis accompanied with enlarged Peyer's patches, solitary lymphatic follicles and mesenteric lymph nodes, and multiple yellowish-white nodules in the spleen and liver were found. Histopathologically, these lesions were necrotizing inflammation containing Gram-negative bacilli. Yersinia pseudotuberculosis serotype 7 was isolated from the spleen and liver. The virF gene, which is an essential virulent plasimid (pYV) in pathogenic Y. pseudotuberculosis isolates, and the ypmA gene, which is a superantigenic toxin, were detected in the isolates. This is the first report of a fatal case of Yersinia pseudotuberculosis 7 infection in the world.