Four studies document underestimations of the prevalence of others' negative emotions and suggest causes and correlates of these erroneous perceptions. In Study 1a, participants reported that their negative emotions were more private or hidden than were their positive emotions; in Study 1b, participants underestimated the peer prevalence of common negative, but not positive, experiences described in Study 1a. In Study 2, people underestimated negative emotions and overestimated positive emotions even for well-known peers, and this effect was partially mediated by the degree to which those peers reported suppression of negative (vs. positive) emotions. Study 3 showed that lower estimations of the prevalence of negative emotional experiences predicted greater loneliness and rumination and lower life satisfaction and that higher estimations for positive emotional experiences predicted lower life satisfaction. Taken together, these studies suggest that people may think they are more alone in their emotional difficulties than they really are.