Background: Hypophosphatemia is one of the common disorders that develop in critically ill patients. It has potential complications and is often unrecognized in those patients. Objective: Determining the incidence of hypophosphatemia in critically ill children, its association with clinical outcomes and the possible risk factors. Methods: 50 patients were enrolled in the study. Levels of serum phosphate were measured on day 1 and day 7 of PICU (Pediatric intensive care unit) stay. The following variables were analyzed: age, gender, diagnosis on admission, malnutrition, phosphorus intake, clinical severity score on admission OFI (Organ Failure Index) and daily scores PELOD (Pediatric Logistic Organ Dysfunction), sepsis, use of dopamine, furosemide and steroids and assessment of nutrition by z scores. Results: The incidence of hypophosphatemia on admission was 42%. On seventh day of admission incidence of hypophosphatemiawas 62%. Malnutritionwas present in 24% of patients, serum phosphorus level was significantly lower in malnourished than in well-nourished children (p value ¼ 0.018). Hypophosphatemia was associated with prolonged PICU length of stay (p < 0.001) but was not associated with increased mortality (p ¼ 0.13). Cases on parenteral nutrition and insufficient oral intake while on mechanical ventilator significantly showed hypophosphatemia (p ¼ 0.017). Hypophosphatemia was associated with the use of furosemide, dopamine, steroids and b2 agonist. Conclusion: Hypophosphatemia was common in the first 7 days of PICU hospitalization and was associated with prolonged PICU stay, Significant association between hypophosphatemia and duration of use of mechanical ventilation, use of furosemide, dopamine, steroids and b2 agonist. © 2017 The Author(s). Published by Elsevier Ltd on behalf of IJS Publishing Group Ltd. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).