The water buffalo (Bubalus bubalus) is important to the economy of several countries, especially in Asia and South America. Little is known regarding the impact of coccidiosis in buffaloes. Cattle and buffaloes are considered to have common species of Eimeria, but critical cross-transmissions have not been made because it is difficult to raise these hosts coccidian free. Clinical coccidiosis was confirmed post mortem in a 22-day-old buffalo calf that died after a 3- to 4-day illness. Oocysts morphologically identical to Eimeria bareillyi were found in the feces and in sections of small intestine. Oocysts were often pyriform, sometimes with asymmetrical sides. The shorter end was flattened and approximately 5–6 μm wide. Unsporulated oocysts in feces were 23.2–29.5 × 16.5–22 μm, with an average of 27.2 × 19.3 μm. Schizonts, gamonts, and oocysts were identified in sections of small intestine where they were located in enterocytes of the jejunum and ileum. No coccidian stages were seen in sections of colon. This is one of the first confirmed cases of clinical coccidiosis in water buffalo.