This paper examines the role of social media in informing corporate decision-making bystudying the decision of firm management to withdraw an announced merger. A standarddeviation decline in abnormal social media sentiment following a merger announcementpredicts a 0.73 percentage point increase in the likelihood of merger withdrawal (18.9%of the baseline rate). The informativeness of social media for merger withdrawals is notexplained by abnormal price reactions or news sentiment, and in fact, it is stronger whenthese other signals disagree. Consistent with learning from external information, we findthat the social media signal is most informative for complex mergers in which analystconference calls take a negative tone, driven by the Q&A portion of the call. Overall,these findings imply that social media is not a sideshow, but an important aspect of firminformation environment.