The European Commission, much like other executives and public administrations in Western Democracies, is frequently faced with leaks. Even though executive leaders often criticize this practice as unwanted breach of confidentiality and secrecy, research has shown that leak prevention is usually not taken seriously beyond public complaints. This paper analyses the phenomenon of leaking in the European Commission and the efforts the Commission makes to prevent leaks from its own ranks. It finds that leaking and leak prevention are regularly discussed at the highest level of the Commission. However, a survey with leak recipients suggest that leaks seem so widely distributed and frequent at various stages of internal decision-making that the existing prevention efforts seem ineffective.Analysing the rules and practices of leak prevention, the paper shows that, while there are anti-leak rules in place, there have been very few cases in which Commission leakers have been administratively sanctioned. The explanation for these observations builds on the argument that leaking is part of regular bureaucratic politics and that leak prevention therefore is not meant to be effective, except for a few important cases.