Online harassment is an emerging global societal problem, with its pervasiveness and persistence creating long-lasting adverse psychological consequences to victims. While many social networking sites (SNSs) have started launching online reporting systems to combat online harassment, surprisingly, little empirical research has examined users’ willingness to use the system for reporting online harassment. In this study, we propose a research model explaining the role of efficacy in using the online reporting system of SNSs to report online harassment. We expect that the results of this study make significant contributions to research and practice.