Open access repositories provide free access to institutional outputs that emanate from researchers and scholars within academic institutions. It is an avenue where intellectual content is collected, stored, preserved, and disseminated to the larger audience of the research community. OAR constitutes national, research, institutional, and subject or disciplinary repositories. With the emergence of OAR, scholars and researchers in academic institutions have the opportunity to avail their intellectual output through a repository hosted by their institutions. Academic libraries are also at the forefront in complementing the effort of their parent institutions by collecting, storing, and preserving the intellectual content of the academics, and making it freely available and accessible to the intended users within and outside academic circle. The paper explores the relevance of academic libraries in the promotion of institutional repositories, with particular reference to Nigerian university libraries. Further, it highlights the emergence of open access movement as a blessing to the Android society. Policies regarding OAR are pinpointed. Open source software used in open access repositories are also identified. The role of academic libraries and librarians in the promotion of OAR in Nigerian university libraries is explicitly discussed. Adaption of institutional repositories in Nigerian universities is fraught with numerous challenges, ranging from lack of awareness, misconception, copyright issues, poor Internet services, and unstable power supply to technical know-how. The paper recommends that for the actualisation of adoption of institutional repositories in Nigerian universities there is a dire need for advocacy and awareness campaigns by librarians on the importance of OAR to the academic community. Effective Internet services and epileptic electric power supply should be improved in Nigerian university libraries to achieve greatness for successful adoption of open access repositories.