Many of the employers fear a reduction in productivity when employees use social networking sites (SNSs) such as Facebook for non-work purposes during office hours. Employers then have started regulating SNSs usage at work, but extreme monitoring and blockage of SNSs can spoil the relationship between employers and employees and can negatively affect organizational knowledge (OK). Therefore, this study investigates the effect of using SNSs on OK by employees at work. Collecting data from employees working in national and multinational organizations and using structural equation modelling for data analysis, the results showed that using SNSs for business activities and for emotional disclosure enhanced OK. In contrast to these findings, work deviation caused using SNSs decreased OK but had no effect on productivity. Finally, the study concluded that the benefits of using SNSs at work are increasingly growing but require transparent policies to reduce employee distractions.