The emergence of Web 2.0 tools has transformed the operation of Knowledge Management (KM) practices in the academic libraries. This study has investigated the application of Web 2.0 tools to enhance KM practices in academic libraries in Tanzania. Eight out of twelve academic libraries located in public universities in Tanzania were purposively selected in this study. The study included two categories of respondents: ordinary library staff and senior library staff (directors, heads of libraries, library managers, and Information and Technology (IT) specialists in the library etc). The findings of the study were determined after applying methodological triangulation within quantitative and qualitative research contexts. This included the use of questionnaires, semi-structured interviews and observations. In the first instance, questionnaires were used to collect data from 278 library staff selected using systematic sampling technique. Interviewing targeted 69 senior library staff was done using purposive sampling technique. In total, 254 (91.4%) ordinary library staff completed the questionnaire; while 57 (82.6%) senior librarians were interviewed. The study findings have indicated the low level of KM application in academic libraries. Muhimbili University of Health and Allied Science (MUHAS) Library showed the strongest application of KM practices, followed by State University of Zanzibar (SUZA) Library. Lack of KM enablers in academic libraries was indicated as one of the significant challenges that hinder the application of KM practices in academic libraries. It was noted that most of the academic libraries visited had websites. On the other hand, the majority of respondents acknowledged that they had personal accounts of the various Web 2.0 tools. The study findings imply that most library staff had some level of experience with a variety of Web 2.0 tools. It was further established that despite the high level of familiarity and use of Web 2.0 tools, respondents were not frequent users of their library websites. The study findings have also indicated a low level of access and use of Web 2.0 tools within academic libraries. Mzumbe University (MU) and SUZA Libraries were the main users of Web 2.0 tools; followed by University of Dar-es-Salaam (UDSM) Library. Knowledge Management System (KMS) Success Model was employed to investigate factors that affect the application of Web 2.0 tools to enhance KM practices. The study findings have demonstrated that the KMS Success Model is suitable for guiding the understanding of the contributing factors with respect to library staff‟s intention to reuse Web 2.0 tools. The study findings supported the KMS Success Model well, whereby seven of the twelve hypothesised relationships were found to be significant. The study recommends that academic libraries in Tanzania should promote and integrate KM practices in their daily operations as well as the use of KM enablers such as; reliable budget, Web 2.0 tools, reliable power supply, internet connectivity availability and adequate ICTs infrastructure. / Information Science / D. Litt. et. Phil. (Information Science)