Background: Ventilator-associated pneumonia (VAP) is the most common health care-associated infection in intensive care units (ICU).Its appearance causes an increase in stay, mortality and economic costs. Probiotics are non-pathogenic micro-organisms that have beneficial effects on human health. We aimed from this work to evaluate the role of probiotic in ventilator association pneumonia prevention. Methods: This was prevention clinical trial study which performed during the period from March 2019 to January 2020 is carried out in Pediatric Department at Zagazig University Hospitals. This study included 80 children that were divided into 2 groups: Probiotic group (40 children). Non-probiotic group (40 children).All subjects in the study were subjected to: Full history. Full General examinations. Laboratory examinations: Patients were randomized to probiotic therapy received Lactobacillus LB corresponding to Lactobacillus delbrueckii and Lactobacillus fermentum 10 billions twice /daily in form of 2 sachets / day throw nasogastric tube till discharge or death. Results: the incidence of VAP among all the studied 80 patients was 44 cases (55 %) most of them were in the control group (72.5%).There was statistically significant difference between the studied groups regarding VAP incidence (lower among probiotic group). There was statistically non-significant difference between the studied groups regarding duration of ICU stay or mechanical ventilation. Conclusion: Using probiotic therapy, In this era of increasing incidence of hospital acquired life threatening infections, may be effective and safe in prevention of VAP but has no effect on duration of MV or ICU stay.