Background: Asthma is a serious global health problem affecting all age groups. Cytokines from T-helper 2 cells are believed to be critical contributors of asthma. Objective: Measuring the serum levels of IL-17 as non-invasive biomarkers to assess asthma severity. Patients and Method: A prospective case controlled study included forty patients were recruited from the outpatient clinic and inpatient of Internal Medicine Department, Al-Hussein University Hospital, Al-Azhar University divided into two equal groups (mild asthma and severe asthma) compared with twenty healthy non-smoker subjects. Total serum level of IL 17 and serum IgE was measured by ELISA technique. Complete blood count (CBC), pulmonary function tests (spirometry) and skin peak test were done for all patients. Results: A significant increase in body mass index (BMI) and age were found in patients with severe asthma compared with those with mild asthma and normal control. Also, patients with severe asthma have more airflow limitation, with a higher serum level of IL-17, IgE, and the number of eosinophils than patients with mild asthma. Significant increase was found in the serum level of IL-17, IgE, the total count of WBCS the number of eosinophils and the number of platelets in asthmatic patients compared with normal control. IL17 has positively correlated with the serum level of IgE, the number of eosinophils, BMI, the age of patients, and negatively correlated with pulmonary function tests. By ROC analysis, a cutoff point for IL – 17 >51.5 Pg/ml, IgE >60IU/ml and the number of eosinophils >2.8% in the mild form of asthma, while the cutoff values for IL17>92.9Pg/ml, IgE>162.0IU/ml and the number of eosinophils >4.1%) in the severer form of asthma. Sensitivity, specificity and positive predictive value for IgE level in mild asthma were 85%, 80% and 77.8% respectively, while in severe asthma 65%, 85% and 83% respectively. Moreover, sensitivity, specificity, positive predictive values for IL17 in mild asthma were 97.5%, 100% and 100% respectively, while in severe asthma were 100%, 100% and 100% respectively. Conclusion: Simple spirometric parameters (bedside test) were a good predictive tool for assessment asthma severity. Among laboratory tests, IL17 was the best biomarker for diagnosis and prediction of asthma severity in asthmatic patients than IgE.