Using principal–agent theory, we explain the effect of an exogenous increase in financial resources on the autonomy of international bureaucracies. This can be empirically demonstrated at the example of the unexpectedly large inflow of fees for the registration of clean development mechanism (CDM) projects and issuance of emission credits on the political influence of staff in the UNFCCC Secretariat. Through document analysis, interviews and econometric analysis, we show that CDM staff was able to gain substantial influence over concrete policy decisions and even change the structure of relevant decision-making and consultation processes. We also show that this may reinforce rather than reduce the role of special interests expressed via country representatives in the CDM Executive Board. While one might be worried about the erosion of democratic principles at the international level, from a normative perspective, the overall effect is difficult to assess. If the international civil service is competent and committed to the delivery of the global public good, its increasing autonomy and influence may also be socially advantageous.