The attractiveness of social networking sites (SNSs) has extended to almost all professionals in numerous human organizations including the library. Librarians as a result of this development are now making use of these sites to connect to other libraries and librarians both within and outside their environment. However, it is observed that the use and benefits derived from social networking sites by Nigerian librarians, generally, and those in academic libraries, particularly, has not been well documented. It is against this backdrop that this study examined the use of social networking sites to both the libraries and the librarians in selected academic libraries in six Nigerian States. A survey research design approach was adopted. The simple random study drew upon 200 academic librarians from academic libraries across six selected States in Nigeria. Five research questions were raised and answered by the study. The results demonstrate that Facebook and Twitter are mostly use by academic librarians. Academic librarians are making use of SNSs on a weekly basis and partially on a daily basis. Many potential benefits of SNSs were indicated both to the librarians and their libraries such as creating opportunity to connect with people across the globe, which includes those that have never been seen and those that one is not sure of coming in contact with. It was also found that SNSs give opportunity for academic libraries to incorporate SNSs as a means of creating more interactive user centered library and information services. Examples of the defects identified associated with SNSs include sexual harassment, cybercrime, fraud, and spreading of spam. It is expected that the outcomes of this study will serve as pioneer data upon which future related studies will be anchored.