Green tea catechins are known as antioxidants beneficial to human health, but they are also defensive compounds produced by tea plants to protect them from herbivores. However, some herbivores can cope with green tea catechins and parasitize tea plants. We investigated the adaptation mechanisms of the spider mite Tetranychus kanzawai, an important arthropod pest of tea plants, to the defensive functions of green tea catechins. The degree of adaptation of spider mites to tea plants was correlated with the intra- and interspecific differences in their behavioral and xenobiotic responses to green tea catechins.