ABSTRACT While fact-checking has received much attention as an important tool to address the prevalence of misinformation, how to ensure fact-checking messages spread as far and wide as misinformation remains to be studied. To fill this gap, this study examined when people decide to share fact-checking messages on social media and what psychological mechanisms underlie such a decision. Two experiments revealed that fact-checking messages debunking a viral misinformation post (i.e. liked, shared, and commented on many times) were perceived to be more socially desirable as compared to fact-checking messages discrediting a non-viral misinformation post. Individuals presumed greater influence of the socially desirable fact-checking messages on themselves than others (i.e. greater first-person perception). Enhanced first-person perception, in turn, led to stronger intentions to share the fact-checking messages on social media. Theoretical and practical implications for fact-checking efforts are discussed.