Cryptosporidium species are the second leading cause of diarrheal disease and death in children of developing countries. This study aimed to determine the prevalence rate of Cryptosporidium among children under 5 years old with diarrhea, who were admitted to a big tertiary hospital in Egypt.This was a hospital-based cross-sectional study involving children 200aged <5 years old in the gastroenterology causality at Cairo University Pediatric Hospital between February 2021 and October 2021. Morning stool samples were microscopically examined as fresh smears and modified Ziehl-Neelsen stained materials.The results showed that all participants suffered from diarrhea <30 months old. A high prevalence 21/200 (10.5%) of Cryptosporidium was detected. But, there was no significant difference between cryptosporidiosis positive or negative cases with respect to stain technique, age, sex, residence, Z-score of weight, symptoms, or stool consistency.