The present study provides evidence of the anti-asthmatic signaling activity of an aqueous fraction of green tea using specific in vitro and in vivo assays in an ovalbumin-induced asthmatic model. Mice sensitized to ovalbumin were orally administered an aqueous extract of Camellia sinensis. The lungs of these mice were then examined by hematoxylin and eosin staining and ELISA analysis to measure cytokine expression. The aqueous extract of Camellia sinensis exhibited potent anti-asthmatic activity by increasing the expression level of tumor necrosis factor-beta and interferon-gamma and decreasing the expression of anti-asthmatic cytokines in the lung. Together, these results indicate that the aqueous fraction of Camellia sinensis is effective in alleviating asthmatic symptoms by increasing the expression of Th1 cell-specific anti-asthmatic biomarkers.