The pathogenesis of allergic asthma is characterized by airway inflammation, eosinophilia, and airway hyperresponsiveness. In the present study, we investigated the anti-inflammatory effects of mastic, obtained from the stem and the leaves of Pistacia lentiscus trees, on allergic asthma. In an ovalbumin-induced mouse asthma model, mastic significantly inhibited eosinophilia, while reducing airway hyperresponsiveness and suppressing the production of inflammatory cytokines (IL-5 and IL-13) as well as chemokines (eotaxin, eotaxin2, and regulated upon activation, normal T-cell expressed and secreted) in bronchoalveolar lavage fluid. Moreover, mastic potently inhibited eotaxin-induced eosinophil chemotaxis in vitro without influencing eotaxin receptor, chemokine receptor 3, expression. These results suggest that mastic may contribute to the treatment of inflammatory diseases.