Policies, such as those on biodiversity and on climate change, promise to create public goods that transcend national borders and generations. Can such policies command popular support across borders? We conduct an economics laboratory experiment run simultaneously and interactively among individuals in Denmark, Spain, and Ghana. The experiment compares private contributions toward a public good that transcends national borders and generations with contributions to a baseline public good that only does one, the other, or neither. Our results show that, in general, when future generations are unaffected by current public good provisions, contributions toward transnational public goods are lower compared to contributions toward national public goods. The effect switches, however, when future generations are affected, suggesting that a focus on future generation impacts may enhance support for transnational public goods.