Background: The most accepted definition of regulatory T cells (T regs ) relies on the expression of several biomarkers, including CD4, CD25, and transcription factor, Foxp3. The T regs maintain tolerance to self-antigens and prevent autoimmune diseases., Aim: The purpose of this study was to determine the difference in natural T reg levels in Entamoeba histolytica, Schistosoma mansoni, Giardia lamblia, Enterobius vermicularis, and Hymenolepis nana infected patients., Setting and Design: Fifty-one pediatric subjects (29 males and 22 females) were recruited from a tertiary care hospital, and were divided into infected and non-infected (control) groups. The mean age of the subjects was 8.7 years., Materials and Methods: Blood samples were collected from infected and non-infected groups, and change in the level of T regs in these subjects was investigated by flow cytometry., Statistical Analysis Used: The statistical analysis of data was performed by SPSS software. Quantitative data used in this study included mean and standard deviation. Data from the two groups were compared by the Student's t-test. The age of the patient and infection status were used for multivariate logistic regression analysis. Odds ratios (ORs) were estimated within a 95% confidence interval, and a P value of <0.05 was considered significant., Results and Conclusions: The levels of natural regulatory T cells, indicated by the biomarkers, CD4 + , CD25 + , and Foxp3 + , increase significantly in patients infected by Entamoeba histolytica, Schistosoma mansoni, Giardia lamblia, Enterobius vermicularis, and Hymenolepis nana as compared to controls. They also increase in cases of mixed infection as compared to infection by a single parasite., Competing Interests: None