Diarrhea is still a public health problem, especially in developing countries. Diarrhea causes morbidity and high mortality in children. Diarrhea can be caused by viruses, bacteria, parasites and food poisoning. One of the parasite that can cause diarrhea is intestinal protozoa. Lately, attention to intestinal opportunistic protozoan infections is increasing. Opportunistic intestinal protozoa infection is an infection by intestinal protozoa that had not considered important and now can cause disease in humans. Cryptosporidium sp, Cyclospora cayetanensis, Isospora belii and Blastocystis hominis are opportunistic intestinal protozoa. The clinical manifestations of the infection depends on the immune status of patients, ranging from asymptomatic in immunocompetent individuals to chronic diarrhea not cured and fatal in patients imunokompromis. This study aims to detect opportunistic intestinal protozoa in children with diarrhea patients in health centers Inpatient Pekanbaru used modified acid fast stain procedure. A total of 76 samples tested positive obtained 22.3% of opportunistic intestinal protozoa found that 9.2% were infected with Cryptosporidium sp, Cyclospora infection were 2.6% and Blastocystis hominis 10.5%, while Isospora not found.