Studies about parasitization by Cryptosporidium in great apes have been scarce and mostly conducted in captivity. The present study reports the presence of Cryptosporidium sp. in wild chimpanzees (Pan troglodytes) from Ugalla, western Tanzania. Ugalla is one of the driest, most open, and seasonal habitats inhabited by chimpanzees. Cryptosporidium sp. was found in 8.9 % of the samples. The presence of the parasite was determined by preserving fecal samples in chemical conventional fixatives (MIF and alcohol absolute) staining them using a modified Zielh-Neelsen technique, and examining them with a light microscope. The number of fecal samples positive for Cryptosporidium was significantly higher during the rainy than during the dry season (p < 0.005). The results showed that feces collected in the rainy season were almost three times more likely to be positive for Cryptosporidium than those collected in the dry season (OR = 2.81). Cryptosporidium detection was significantly negatively affected by highest temperatures (>28.7 °C, p < 0.001). Cryptosporidiosis can cause serious health problems in humans and its potential effect on Ugalla chimpanzees is discussed.