Recent studies indicate that Protestant theological conservatism is associated with lower levels of generalized trust. In this article, we ask: What are the implications of theological conservatives’ lower trust levels? Specifically, does their lower trust impact environmental cooperation? Past research finds that trust promotes cooperation, and we theorize that because theological conservatism undermines trust, it should negatively impact cooperation directly. Thus, we suggest an interaction between trust and theological conservatism on cooperation. We test the arguments in the context of environmental social dilemmas, including decisions about recycling, water and energy consumption, and individuals’ willingness to protect the environment, using data from the 2010 General Social Survey. Our results support the theory that trust levels among Protestant theological conservatism more acutely undermine environmental cooperation, and we further discuss the implications of these findings.