Recent research has discovered that users of popular social networking site Facebook tend to underestimate their audience size, that is, the number of friends who have viewed their posts. This study investigated whether correcting people’s misperceptions of their audience size would lower their satisfaction on the four fundamental needs outlined by Williams (1997), negatively impact their affect, lead to feelings of rejection, and reduce their satisfaction with their recent Facebook posts. Upon being made aware that their true audience size is larger than they would estimate, individuals are faced with the idea that more people see their posts, but do not provide feedback on them. Attachment anxiety was also looked at as a potential moderator of the effect of audience size, as individuals with high attachment anxiety are especially sensitive to signs of rejection. A total of 187 participants were randomly assigned to either be made aware of their true audience size being larger than they would typically estimate, or not. Participants viewed their most recent posts on Facebook, and then filled out the dependent measures in an online survey. Limited support was found for our main hypothesis, as increasing the perceived audience size only had an effect on participants’ negative affect, and none of our other measures of interest. Attachment anxiety did not moderate the impact of perceived audience size, and exploratory analyses suggested that trait self-esteem may instead be a potential moderator of this effect. Despite finding only minimal support for our hypotheses, we believe that future studies may find our predicted effect, by utilising a more direct manipulation of audience size. Suggestions for directions for future research to take are brought up in the discussion.