This study analyses how readers impute credibility to the Tanzanian investigative newspaper Raia Mwema which, as a matter of routine journalistic practice, uses a high number of anonymous sources. Against the backdrop of a strong theoretical position, espoused by media studies theorists in both Western media contexts and in Africa, in which this practice is deemed to diminish the credibility of both journalists and their stories, the study’s main purpose is to examine how readers make sense of this very prevalent practice in a country that has recently opened up to media plurality. It also investigates where they locate the source of credibility for this high-selling newspaper, if not in the traditional way through its named sources of information. The study surveys the frequency of appearance of anonymous sources in this newspaper for the period of one year from January 2011 to December 2011. Then the study considered how this practice is viewed and understood by the wider journalistic community in Tanzania as well as looking into how the journalists and owners of Raia Mwema make choices about attributing their journalism. Lastly, the study engaged with particular readers to understand what sense they make of this practice in the wider landscape of Tanzanian media and the post-repressive political situation. The study makes use of theories of the sociology of news production so as to understand the context in which Raia Mwema has routinised the practice of anonymous attribution and whether the journalistic community and newspaper readers find the practice credible. The study also employs reception analysis in order to understand to what extent Raia Mwema readers negotiate and make sense of the mainly political, and often critical, media messages they get from newspaper. In this way, it introduces the importance of the reader in the production of meaning and of assessment of credibility of journalism. The interviews – ranging from journalists working at the paper, through the wider journalistic community and taking in the readership of the paper – show that theoretical considerations of journalistic credibility must take into account the political, social and media context in which journalism is produced. Pronouncements on the overuse of anonymous sources, without understanding the way readers and journalists negotiate the complexities of an actual situation, do not tell us much about credibility and how readers understand the messages they are given. From this study, it is clear that in African countries embarking on opening media systems, credibility involves more factors than have been discussed in the literature and that readers and journalists are sophisticated consumers and producers of media messages in countries that place a host of obstacles in the way of investigative journalism and open political communication.