Global agriculture consumes substantial resources and produces significant pollution. By shifting its production to new locations, and inducing changes in technology and input use, trade has a substantial impact on environmental sustainability of the world's food systems, but due to suboptimal environmental policy, the exact nature of these impacts is in dispute. We review the literature on agricultural trade and environmental sustainability, highlighting the different approaches taken in ecology versus economics. While useful in identifying environmental costs, much of the ecological literature does not compare these costs to a trade-free counterfactual and can therefore be misleading. Further, by moving production to places with more resources and increasing production efficiency, trade can reduce the environmental impact of food production. On the other hand, trade can also limit the effectiveness of domestic environmental policy because production can be shifted to countries with less stringent regulations. However, recently, consumers are leveraging trade policy to induce exporters to improve environmental sustainability. While such policies are gaining traction in wealthy countries, evidence suggests that such measures will not reach their potential without buy-in from decision makers in the countries where the environmental damages are occurring.