Previous studies find that adopting Freedom of Information (FOI) laws increase reporting of corruption, as this facilitates the right of access to governmental information. Thus, it is argued that FOI laws increase transparency and enhance government accountability. However, whether or not adopting such transparency laws improves bureaucratic efficiency remains unexplored. We provide first quantitative evidence on the impact of FOI laws on bureaucratic efficiency. Using panel data on 132 countries from 1990 to 2011, we find that adopting FOI laws, and in particular 'stronger' FOI laws, is associated with an improvement in bureaucratic efficiency, after controlling for self-section bias. FOI laws appear to be more effective in the long run, and if combined with a higher degree of media freedom, presence of non-governmental organization activism, and political competition. These findings are robust to controlling for endogeneity using instrumental variables, alternative samples, and estimation methods.