Background: There is increasing evidence that lactate and hyperlactatemia can be a marker for the outcome in critically ill children. Objective: Our study aimed to describe the prognostic value of increased serum lactate in critically ill children and its association with worse outcome. Patients and methods: This prospective observational (cohort) study was carried out in Pediatric Intensive Care Unit (PICU) and Clinical Pathology Department at Zagazig University Hospitals over a period of 6 months started from august 2018 till January 2019, it included 86 critically ill children. The study was approved by Ethics Committee, Faculty of Medicine, Zagazig University. Results: Serum lactate was significantly higher among died cases than survived. Conclsuion: Hyperlactatemia in critically ill children is associated with worse outcome in critically ill patient in PICU.