Background: Allergic rhinitis (AR) is a common allergic disease. It has a marked effect on quality of life. Various populations of effector and regulatory T cells and their cytokines play a crucial role in allergic inflammation. Objectives: This study was designed to evaluate serum levels of IL-9 in subjects with allergic rhinitis and to investigate the association of its serum level with the severity of the disease, and its clinical parameters. Methodology: This study included 19 AR cases and 19 healthy controls. All patients and controls were subjected to the followings: full medical history, allergy skin test, nasal smear to detect eosinophilia, and measurement of serum levels of IL-9 by enzyme linked immune-sorbent assay (ELISA). Cases were classified according to Allergic Rhinitis and its Impact on Asthma (ARIA) guidelines into mild, moderate and severe. Results: The median values of serum levels of IL-9 in AR cases were higher than in the controls (8.5 vs 6.85 pg/ml) with statistically significant difference (p =0.02). Roc curve analysis, also showed significant association between the serum level of IL-9 in AR patients than controls (P value < 0.0001), the cut point was >7.5 pg/ml in AR patients with sensitivity and specificity of 77.78 and 83.33 % respectively. In addition, there was a significant association between the serum levels of IL-9 and degree of disease severity (P=0.01), and AR symptoms (nasal obstruction and irritative symptoms). There was a significant association between sensitization to multiplicity of allergens and the mean level of IL-9 in AR cases (P< 0.05). Conclusion: The elevated serum level of IL-9 in AR cases may provide new insight into the patho-physiology of the disease and into development of novel therapeutic targets.