In 2009, experimental Cyclospora infections were established in two juvenile female and two adult male Cercopithecus aethiops (African green monkeys) at Nairobi’s Institute of Primate Research (IPR). The study animals were humanely sacrificed, and gross and histopathological evaluation was done at seven weeks post-infection. On gross examination, the juveniles had no abnormalities except for a slight enlargement of the mesenteric lymph nodes, while the adults displayed more pathology of enlarged lymph nodes, hemorrhagic gastrointestinal tracts, widespread necrotic foci of the liver, and enlarged spleens. Significant histopathological findings were observed in both the juveniles and adults, which ranged from mild inflammatory reactions in the stomach and intestines to intense cellular infiltrations with mitotic activity and lymphocytic infiltrations around the periportal area of the livers. The lymph nodes had extensive hyperplasia with many mitotic cells.