Today, the open access movement is a revolutionary and effective movement that is popular in scientific societies. The nature and goal of this movement, i.e, open access to scientific findings have a close relation with the major goal of libraries and librarianship, i.e., information accessibility to users without any censorship or bias. The well-known sources of open access movement are: open access archives and repositories, E-prints and open access journals. One of the open access archives and repositories is institutional repositories. This source is a carrier that recognizes, registers, organizes and preserves the digital output and make it accessible to all.In this article, after a brief discussion about open access movement and its resources, institutional repositories are defined as a modern and effective tool to institutional information accessibility.The features, existential philosophy, content, benefits and challenges of these resources are also discussed.Some of the famous open access softwares that are needed to create the institutional repositories are introduced and finally discussed about the role of libraries and librarians as a chief people responsible to collect and provide access to institutional information in creation and promote the use of this resources.