Abstract: The present study was conducted on 571 buffalo calves from different Egyptian governorates (Cairo, Giza, Beni Suef and Qualiobya) around the year. Four age groups were involved; less than one month, from 1-2 months, from 2-6 months and more than 6 months of age. Modified Ziel-Neelsen staining technique (MZN) was used for the detection of Cryptosporidium oocysts in formed and diarrheic fecal samples. Blood samples were collected for biochemical analysis. Prevalence of Cryptosporidium infection among buffalo calves was 52%. The highest rate of infection was in animals aged less than 1 month (62%) The lowest rate of infection was reported in buffalo calves aged more than 6 months (46%). Regarding seasonal prevalence, Cryptosporidium infection was higher in spring (58%) followed by winter (55%) then, autumn (50%) while, the lowest rate was in summer (43%). Dealing with biochemical changes, the infected animals showed significant increase in serum urea and creatinine than healthy ones. In conclusion, Cryptosporidiosis had a relationship with age and seasonal variations. Also, it had an adverse effect on biochemical parameters of infected buffalo-calves.