This paper attempts to describe the public library system's role in Nigeria towards the creation of social capital for sustainable development in the knowledge society. It highlights concepts of social capital, knowledge society, and the public library system in Nigeria and its situation. The paper indicates a number of strategies for the generation of social capital by public libraries that include organising programs for children (quizzes and debates), provision of internet-based services, conducting film show programs, organizing voter education programs, collaborating with voluntary associations and organizations, and provision of universal services, among others. It identifies the lack of a proper meeting hall/ room to host or organize community meetings; non-availability of open space for festivals, and social gatherings; traditional library layout and un-conducive atmosphere of the library environment to provide library programs and activities; and lack of community awareness of library functions and services. Inconvenient distance between the library and the community members, inadequate and out-of-date library collections, inadequate ICT infrastructure/ facilities for library services and programs, and lack of library understanding and its role in the services contributing to social capital creation as the challenges in the generation of social capital by public libraries for sustainable development. Finally, the paper came up with suggestion for the creation of social capital by public libraries.