In this paper, two claims are made. The main claim is that a fruitful approach for theorizing the political legitimacy of global governance and the proper normative role of civil society actors is the so-called 'function-sensitive' approach. The underlying idea of this approach is that the demands of legitimacy may vary depending on function and the relationship between functions. Within this function-sensitive framework, six functions in global governance are analyzed and six principles of legitimacy defended, together constituting a minimalist account of political legitimacy. This account suggests that civil society actors may strengthen political legitimacy by performing five of these functions under certain conditions and insofar as the proposed normative political principles are fulfilled: problem identification, agenda-setting, implementation, enforcement and monitoring, and evaluation. The second claim is critical and is chiselled out against the backdrop of this function-sensitive account, through which I demonstrate that much vagueness and confusion with regard to the proper role of civil society actors for strengthening the political legitimacy of global governance could be traced to the so-called 'transmission belt' model, which has gained popularity in international political theory. This model depicts civil society as a transmission belt between the public sphere and decision-making loci, where it is assumed that civil society actors contribute to the strengthening of political legitimacy by transmitting peoples' preferences, beliefs, and opinions from the former to the latter space by indirectly or directly influencing the decision-making. It is argued that this picture is misleading and generates erroneous prescriptions of how civil society actors should act to increase political legitimacy.