Academic staff members encourage university students to use online student discussion boards within learning management systems to ask and answer questions, share information and engage in discussion. We explore the impact of anonymity on student posting behaviour. An online survey was completed by 131 second year undergraduate psychology students (91% response rate). Overall, students reported being significantly more likely to post to discussion boards when anonymous posting was enabled than when identified posting was required ("d" = 0.49). Students who preferred to post anonymously were significantly less likely to post on discussion boards requiring identification than other students ("eta"[superscript 2] = 0.27). The experimental manipulation of anonymous/identified postings using a simulated discussion board thread revealed no significant differences in the perceived credibility of authors of anonymous and identified messages, or in the likelihood of responding to these messages. A combination of individual level factors; including online privacy concern, self-consciousness and self-efficacy; were predictive of the likelihood of making identified postings ("R"[superscript 2] = 0.387), but only self-efficacy was a significant unique predictor of anonymous postings ("sr"[superscript 2] = 0.05). Educators can consider enabling anonymous postings and providing training to increase student self-efficacy as ways of increasing student engagement through decreasing concerns about self-presentation online.