Background: Irritable bowel syndrome (IBS) is a group of diseases of the gastrointestinal tract (GIT) with a heterogeneous pathophysiology and unclear role for intestinal parasitic infections. Objective: The aim of the current study was to detect the relationship of parasitic infection with malnutrition among cases of IBS. Patients and methods: A cross sectional study was conducted and included 120 children in age from 5 to 15 years old attending the outpatient clinics in October 6 University Hospital and Primary Healthcare centers with GIT symptoms suggesting IBS. All cases subjected to medical evaluation, anthropometric assessment and stool analysis. Result: The study revealed that 68/120 (56.7%) of IBS cases had parasitic infection (Group A) with Giardia lamblia stages is the most frequent one (25/68 samples, 36.7% of group A, and 20.8% of total IBS case). IBS- diarrheic type (IBS-D) was the predominant subtypes (54/120, 45%) and associated with parasitic infection (P-value <0.05) that wasn't observed in other subtypes. The most frequent form of malnutrition according to the Egyptian Z score was overweight (19/120, 15.8%) of IBS cases and no cases with undernutrition or obesity. No significant relation between parasitic infection and malnutrition in IBS (P-value >0.05) for all parameters. Conclusion: Parasitic infection is common among cases of IBS and associated with diarrhea. Overweight is the most frequent form of malnutrition in cases of IBS even in presence of parasitic infection that revealed no association of parasitic infection with undernutrition in cases of IBS.