Enterotoxigenic Clostridium perfringens was associated with diarrhea in a 4-yr-old female captive-bred red-footed tortoise (Geochelone carbonaria). Diagnosis was based on bacterial culture, detection of C. perfringens enterotoxin in feces, and exclusion of commonly recognized pathogens. After treatment with metronidazole, normal feces were passed and C. perfringens enterotoxin was no longer detected in the feces. Although the role of C. perfringens cannot be determined definitively from this case, this pathogen should be considered in cases of diarrhea in tortoises and, perhaps, other reptiles.