Objectives: Allergy has been described as an inflammatory with hypersensitivity resulting from seasonal or perennial responses to specific allergens. The root of Platycodon grandiflorum (Jacq) A. DC.(Platycodi Radix; Campanulaceae) has been traditionally used to treat chronic diseases such as bronchitis, asthma, pulmonary tuberculosis, inflammation and hyperlipidemia. In this study, we examined the effect of 70% ethanol extract of Platycodi Radix (PR-E) on ovalbumin (OVA)-induced airway inflammation in mice. Methods: Mice were sensitized and challenged by OVA inhalation to induced chronic airway inflammation, and then were intragastrically administered PR-E extract at doses of 50 and 200 mg/kg/day from days 21 to 30 consecutively. The levels of allergic mediators such as histamine, OVA-specific immunoglobulin (Ig) E, and cytokines such as IL-4 and IFN-γ were measured in the sera of mice by ELISA. The histological change of lung tissue was observed by hematoxylin and eosin (H&E) staining. Results: PR-E extract significantly decreased the serum levels of histamine, OVA-specific IgE, and Th2 cytokine, IL-4 compared with those in the OVA-induced group. PE-E extract significantly increased the serum level of Th1 cytokine, IFN-γ. Based on lung histopathological studies, inflammatory cell infiltration and mucus hypersecretion were inhibited by PE-E extract administration compared to that in the OVA-induced group. Conclusions: These findings indicate that PE-E extract may be useful as an adjuvant therapy for the treatment of bronchial asthma.