This book chapter examines the role and influence of non-state actors in global environmental politics. It draws on the theoretical framework of multilevel governance, emphasising the influence of non-state actors at various policy-making levels. Empirically, we assess and compare the following cases: multilateral environmental negotiations (the climate change negotiations and the International Whaling Commission – IWC), the EU Emissions Trading System (ETS), and social and environmental certification programs. The comparison across cases reveals that there is significant variation in both the role and influence of non-state actors in multilateral, EU-level and private governance programs. Careful attention to this variation is crucial for advancing our understanding of how and under what conditions non-state actors influence policy outcomes. We argue that the influence of non-state actors is closely related to the authority and competence of nation states. Moving from multinational to supranational and transnational rulemaking, the cases show a declining role of nation states and increasing role of non-state actors. Moreover, in all three cases, we see that because rulemaking is an ongoing and iterative process, the goal attainment and influence of various actor groups change over time.