Even though existing studies have shown the positive effects of social network sites (SNSs) on learning behaviors and outcomes, how SNS can cause learners to develop negative perceptions about their learning activities is still understudied. Here we report a one-of-a-kind study that examines the negative impact of privacy concern on students' learning behaviors online while using SNSs. Based on the stimulus-organism-response (SOR) paradigm, our study focuses on how privacy concern develops knowledge hiding perceptions of the learners, thereby affecting their online collaboration. Further, our study also explores the moderating role of perceived supervisory support between the relationship of privacy concern and knowledge hiding perceptions. Participants in the study were 282 students pursuing their studies in several higher educational institutions in China. Our findings show that two types of privacy concern (abuse of knowledge and unauthorized access to private data) can positively influence students' knowledge hiding perception, which subsequently can negatively affect their participation in online collaborative learning. On the other hand, perceived supervisory support only moderates the relationship between privacy concern about abuse of knowledge and knowledge hiding perceptions. Based on these findings, we draw practice implications for supervisors and students in Universities.