Background: Chitinase-Like protein YKL-40 is secreted from neutrophils, macrophages and airway epithelial cells of the respiratory tract mucosa. Therefore, it can act as a specific biomarker of granulocyte function and macrophage activation in patients with asthma. This study aimed to investigate the association between serum levels of YKL-40 and asthma in Sharkia Governorate. Methods: This case-control study was carried on 60 children; 30 asthmatic child with confirmed reversible, expiratory airway obstruction with clinically and Spirometric-based diagnosis of asthma and were further classified into 3 subdivide group according to Levels of asthma control in children adopted from the Global Initiative for Asthma GINA 2015 and 30 healthy age and sex matched child as control group who were admitted to paediatrics pulmonology department and outpatient clinic at zagazig university hospital during the period from October (2018) to April (2019). Results: There was a high statistical significant difference between asthmatic and non-asthmatic groups in YKL40 level which was higher in asthmatic group than non-asthmatic group and there was a significant correlation between the levels of serum YKL-40 with the ratio of peripheral blood eosinophils. Conclusion: The high levels of serum YKL-40 correlated with the diagnosis of asthma in children.