Since information sharing is achieved in cooperation with others, not just by oneself, social networking sites (SNSs) based on extensive social networks are an ideal environment for sharing information. In particular, SNSs’ network externalities are crucial to the success of the information and communication technologies industry. Thus, this study investigated how SNSs’ network externalities affect users’ perceptions of benefits, satisfaction, and restaurant information-sharing intentions. This study found that perceived network size and perceived complementarity significantly influenced perceived usefulness. Furthermore, perceived referent network size, perceived complementarity, and perceived compatibility significantly influenced perceived enjoyment. In addition, perceived benefits significantly influenced satisfaction, which in turn significantly influenced restaurant information-sharing intentions on SNSs. These findings have considerable implications for understanding the role of SNSs’ network externalities in sharing information.