In this study the evolution of Eimeriosis in naturally infected calves was analyzed during 23 days starting at birth. The specie E. bareillyi was first identified in feces culture. Later other species of Eimeria already described in water buffalo were identified. The animals which died were submitted to necropsy, revealing macroscopic lesions in the ileum region. Histological analyses of the ileum region showed acute necrotic enteritis and the presence of Eimeria sp. in different developmental stages. Early infection by this parasite could be responsible for a secondary bacterial infection trough the intestinal lesions. The utilization of prophylactic medication and the therapeutic treatment of clinical Coccidiosis in water buffalo calves are necessary to their satisfactory development and surveillance.