The purpose of the current work is to examine when and how knowing collective opinion influences people’s judgments and decisions in social media environments. In particular, the present work focuses on people’s true-false judgment of statements found on websites and the likelihood of sharing these statements. The results from Experiment 1 revealed that, for false statements, collective opinion had little influence on people’s true-false judgments, but, for true and debatable statements, their judgments were biased toward collective opinion. The results from Experiment 2 indicated that the likelihood of sharing the true, debatable, and false statements followed the collective opinion, and that people were less likely to share false statements than debatable or true ones without collective opinion. These findings extend past work on social influence and advance understanding of how people make judgments and decisions in social media websites.