Recent research suggests that consumers often exhibit the "commonness fallacy" by overestimating the likelihood of others choosing a frequently consumed item (e.g., vanilla ice cream) rather than a less frequently consumed item (e.g., tiramisu). This research tests whether the extent to which consumers perceive their choices as similar to others-their social projection tendency-explains the commonness fallacy.Two preregistered studies (N = 605) found that consumers with a higher social projection tendency overestimated the extent to which others would choose commonly consumed options if they themselves chose such options over less commonly consumed options. However, social projection cannot fully explain the commonness fallacy as participants with lower social projection tendencies also displayed the commonness fallacy in both studies. The findings delineate the commonness fallacy from consumers' well-documented tendency to view others' choices as similar to their own.