Background: Acute respiratory failure in children, often due to pneumonia and bronchiolitis, commonly leads to acute lung injury (ALI) and pediatric acute respiratory distress syndrome (PARDS) in Pediatric Intensive Care Units (PICUs). The neutrophil-to-lymphocyte ratio (NLR) is a potential prognostic marker for these conditions. This study aimed to evaluate NLR as a predictor of disease severity and outcomes, including mechanical ventilation and mortality, in pediatric chest infections in the PICU. Methods: This cross-sectional study included 100 children admitted to the PICU at Benha University Hospital for chest infections. Clinical data, lab results, and outcomes were assessed for each patient. Results: Of the 100 children (56 males, 44 females), pneumonia was diagnosed in 70%. NLR was significantly higher in patients needing mechanical ventilation (p < 0.001) and those who died (p < 0.001). NLR correlated positively with CRP, CO2, and hospital stay duration, and negatively with platelets, pH, and HCO3. ROC analysis showed an AUC of 0.876 for predicting mechanical ventilation and 0.950 for predicting mortality, with high sensitivity and specificity at cutoffs of >5.1 and >5.9, respectively. Conclusion: NLR is a valuable, rapid, and cost-effective prognostic marker for predicting the need for mechanical ventilation and mortality in children with chest infections in the PICU.