We examined stool samples for trophozoites of the entodiniomorphid ciliate Troglodytella abrassarti Brumpt and Joyeux, 1912, from a habituated group of chimpanzees (Pan troglodytes schweinfurthii) at Mahale Mountains National Park in western Tanzania. In our study, fresh fecal samples from identified individuals were collected immediately after defecation and fixed in 10% formalin. In total, 52 samples from 38 chimpanzees (61% of 62 chimpanzees in the group) were examined using a direct smear method. A stool sample from an individual collection date from an individual chimpanzee was examined up to 3 separate times before it was called negative. Forty-eight (92%) of the 52 samples were positive, and stools from 37 (97%) of the 38 chimpanzees were positive for trophozoites of T. abrassarti. The high prevalence of T. abrassarti in these chimpanzees is consistent with previous reports of this organism in chimpanzees.