For scholars of global environmental politics, transnational actors are a central focus, and many ascribe significant influence to them. However, it is not always clear how their influence is felt or what strategies are most effective. Most studies that do consider these issues focus on the influence of either environmental non-governmental organisations (NGOs) or business groups on one international outcome. Very few studies analyse these actors together. This limits the generalisability of conclusions. Remarkably, almost none of this work has considered the influence of these actors and the strategies they could employ in prolonged environmental negotiations that last many years or decades. Drawing on a rich empirical data set from the international climate negotiations, both are addressed. How the influence of transnational environmental NGOs and business groups is felt in long negotiations is considered, and three strategies are identified that these actors can use to influence not only state behaviour but each other as well.