Fostering international environmental cooperation requires understanding and addressing the influences of national policies on environmental performance. This Article focuses on one potential influence, namely, social policy. Drawing on multiple disciplines, the Article offers an analytic model to explain connections between social policy and environmental performance, with a particular focus on GHG emissions performance. It shows why social policy should improve the environmental performance of nations. The Article also presents theoretical reasoning for potential differences in the effects of social policy on environmental performance, depending on the relevant categorization of the latter as human, ecological, or global. Particularly the effect of social policy on GHG environmental performance is related to its level of global connectedness.