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 childhood asthma. Methods: This case-control study was carried out in our department of pediatrics, Zagazig university hospitals during the period from October (2018) to April (2019). A total of 60 children were recruited in our study; 30 asthmatic children with confirmed reversible, expiratory airway obstruction with clinically and spirometric-based diagnosis of asthma and another group had included 30 healthy age and sex matched children as control group. Results: There was statistically significant difference between asthmatic and non-asthmatic groups regarding YKL40 levels which was higher in asthmatic group than non-asthmatic group Conclusion: The high levels of serum YKL-40 correlated with the diagnosis of asthma in children.