Green political theory has yet to be fully developed as an approach to international relations and international political theory. This dissertation explores green political theory for international theory implications and tests a hypothesis derived from ecological thought. In testing whether more sustainable countries are more peaceful (less aggressive) than less sustainable countries, this dissertation argues that green theory can provide substantial insight into the study of world politics. Specifically, green theory provides the insight that the conditions of human relationships inform and are informed by the natural environment. This dissertation further concludes that policies aimed at sustainability may provide a strong basis for an increased world peace, but that this hypothesis requires further study. In doing so, this dissertation validates a working model of green theory for future research at the same time it registers an evolving conception of global environmental and human security.