Cost-effective and equitable climate change mitigation requires the transfer of resources from developed to developing countries. In two behavioral experiments, we demonstrate that American subjects act according to a strong home preference, by making private donations and writing letters in support of public spending more often for mitigation programs located at home versus those overseas. We attempt to overcome the preference to act at home by randomly informing some subjects that foreign programs are more cost-effective than domestic programs. Home preference is mitigated only in the case of private donations. From a separate experimental treatment, we show that the preference against foreign programs is exacerbated when the co-benefits of mitigation programs are made salient. Importantly, home preference crosses party lines, indicating that it is a deep-seeded, affective preference. These findings highlight significant political obstacles to international cooperation on climate change that relies on transfers.