Background: Dehydration is a major cause of preschooler illness and death throughout the world it is often a result of diarrheal disease in children. The aim ofthisstudy was to evaluate the effect of educational intervention on nurses' performance about management of dehydration for children under five years. Subjects and method:A quasi-experimental research design was used. Eighty nurses who was working at Pediatric out-patient clinics and pediatric medical department and eighty children who had dehydration.Three Tools were used for data collection:Structured interview Schedule, Nurses' practice observational checklist, Health assessment related to nursing management of dehydration for children under five years.Management and administration of oral rehydration solution. Results:The present study revealed that, only 5.0% of nurses had good knowledge scores and 95.0% of them had satisfactory practices before the program intervention while this percentage improved to 100% of them immediately and one month after the program intervention Conclusion:A significant difference between total scores of nurses' knowledge and practice before and after educational intervention. Recommendation: In-service educational training program should be provided to all pediatric nurses about management of dehydrationfor children under five years to update their knowledge and clinical practice.