Rationale: Airway remodeling is an important feature of chronic asthma that causes irreversible airflow obstruction. Although asthma is considered to be a Th2 disease, the role of T-bet and GATA-3, the key transcription factors for differentiation toward Th1 and Th2 cells, in the pathogenesis of airway remodeling is poorly understood. Objectives: We therefore examined the effects of GATA-3 or T-bet induction of Th1/Th2 bias on the development of airway remodeling in mice. Methods: The development of airway remodeling after repeated allergen challenges was analyzed using transgenic mice overexpressing either GATA-3 or T-bet. Main Results: The degrees of subepithelial fibrosis and airway smooth muscle hyperplasia after repeated allergen exposure were significantly enhanced in mice overexpressing GATA-3, compared with wild-type mice. Allergen-induced goblet cell hyperplasia and mucus hypersecretion were significantly lower in mice overexpressing T-bet than in wild-type mice. Eosinophilic airway inflammation increased in mice overexpressing GATA-3, but decreased in mice overexpressing T-bet after repeated allergen exposure. Cytokine analysis revealed that the Th1/Th2 cytokine balance shifted to Th2 in lung homogenates and lung T cells of mice overexpressing GATA-3, whereas this balance shifted to Th1 in those of mice overexpressing T-bet after allergen exposure. Lung transforming growth factor- and eotaxin levels were associated with the degree of subepithelial fibrosis and eosinophilic airway inflammation, respectively. Conclusions: Overall, the results indicate that development of airway remodeling is regulated by the lung Th1/Th2 bias induced by GATA-3 and T-bet.