We contribute to the growing literature on how political support for domestic policies that contribute to global collective goods is impacted by other countries’ policy actions. To do so, we focus on carbon taxation, one of the most important yet contested policy instruments for mitigating global warming, in the world’s third largest economy, Japan. Using a combination of two experiments embedded in a representative public opinion survey, we examine arguments relating to how the adoption and level of ambition of other countries’ carbon taxes affect the public’s preferences for current and future carbon tax designs. We find evidence that the choices of other countries affect both support for carbon taxation and preferences over its design. More ambitious carbon pricing in other countries increases support for carbon taxation, while less ambitious pricing reduces support. Moreover, information about lower carbon prices in other countries decreases support more than other countries having no carbon taxation at all. Public support for more stringent domestic carbon pricing thus hinges on the policy choices of other countries, contrary to other environmental issues. Our research also shows, however, that particular domestic policy design choices can help in mitigating otherwise negative effects of non-cooperative behavior by other countries.