AbstractWhile prior work suggests the significant role virtual influencers (VIs) can play in addressing social and welfare issues, it remains unclear how they can increase social media users' engagement in prosocial behaviors. The current study examines the role of influencer flattery in driving the prosocial behavior of social media users. Specifically, the research investigates how flattery and humanlike appearance influence the perceived authenticity of VIs and the subsequent prosocial behavior of social media users (Studies 1 and 2). Furthermore, the research substantiates these effects by exploring how flattery and anthropomorphism via humanlike traits impact perceived authenticity and prosocial behavior when social media users witness the influencer praising others (Study 3). Beyond intention to donate (Study 1), the study also investigated its impact on related prosocial behaviors, such as click‐through behavior (Study 2) and the willingness to pay for fundraising merchandise (Study 3). The findings of this research offer concrete implications for nonprofit organizations by demonstrating the persuasive impact of flattery, perceived authenticity, and anthropomorphism in mobilizing public support, donations, and merchandise purchases for social causes.