Much of our cultural heritage owes a large debt of thanks to private collectors of manuscripts, incunabula and printed material; to those individuals who were interested in the accumulation of knowledge and the preservation of our literary history, and who saw fit to pass on their acquisitions for the foundation of libraries. Across Africa, libraries are contributing to development in their countries. However, this work remains largely unrecognized by contemporary library users. To bridge this gap, this paper examines the unique role of private libraries in preserving the cultural heritage and the sustenance of indigenous knowledge in Nigeria. It further discussed the importance of cultural and knowledge sustainability, which has become a growing priority in sustainable development agendas, being depicted as a fourth pillar, equal to social, economic, and environmental concerns. It argues that more explicit coverage of cultural and knowledge sustainability is required to not only improve the contributions of private libraries to culture and knowledge sustainability, but also to provide an increased understanding and appreciation of the value of private libraries.