Background: Reactive thrombocytosis (Platelets >500K/μl) is estimated between 3-13% in hospitalized children and has been associated with RSV infection and younger age. We aimed to examine the clinical significance of thrombocytosis in children admitted to the hospital with an influenza-like illness (ILI). Methods: We performed an analysis of a database of patients evaluated at our Medical Centers with an ILI between 2009 and 2013. We included pediatric patients and examined the association between platelet count, respiratory viral infections, and admission outcomes (hospital length of stay (LOS) and admission to the pediatric intensive care unit (PICU() using regression models adjusting for laboratory, clinical and demographic parameters. Results: Of 19,192 adults and children in the database, 5,171 children met inclusion criteria (median age 0.8 years (Interquartile range, 0.2-1.8), 58% male, median LOS of 3 days (Interquartile range, 2-5)). Younger age and not the type of viral infection was associated with a high platelet count (p<0.001). Elevated platelet count independently predicted admission outcomes, adjusted for multiple covariates (p≤0.006). Furthermore, the presence of thrombocytosis was associated with an increased risk for a prolonged LOS (odds ratio=1.2 (95% Confidence interval=1.1-1.4, p=0.003)) and admission to the PICU (odds ratio=1.5 (95% Confidence interval =1.1-2.0, p=0.002)). Conclusions: In children admitted with an ILI, a high platelet count is associated with younger age and is an independent predictor of hospital LOS and admission to the PICU. Our results show that platelet count may be used to improve risk assessment and management decisions in these pediatric patients.