The notion that a strong civil society helps to fight corruption has become a cornerstone of governance policy. Yet, a continuing dearth of empirical research, which tests this general proposition and probes the relevant causal mechanisms, feeds rising skepticism of current policy initiatives. This study theorizes the relationship between civil society and corruption, arguing that civil society's impact depends to a large extent on its ability to generate sufficient public pressure which, in turn, depends on the press being free. Analysis of cross-national and longitudinal data shows that civil society strength is indeed inversely linked to the level of corruption, but the impact is highly dependent on press freedom. This conditioning effect affirms the importance of the public pressure mechanism. These results explain the need for policy to target both civil society and press freedom in promoting accountable governance and sustainable development.