<p>With widespread social media adoption, online charitable platforms have expanded significantly. These platforms typically emphasize recipients’ hardships and transformations to encourage donations, but the effectiveness of these messaging strategies remains unclear. Drawing on narrative persuasion and social exchange theories, this research examines the impact of aligning the valence of recipients’ attitudes toward their plight with contrast effects on public participation intentions through three experiments. The results reveal that: (1) When narrative messages portray the recipient’s positive attitude toward their plight, those with a contrast effect significantly increase intentions to donate and disseminate; in contrast, when the narrative messages depict the recipient’s negative attitude toward their plight, those without a contrast effect significantly enhance donation intention; (2) perceived social image and perceived efficacy serve as mediating factors; and (3) self-other overlap moderates these relationships, with significant effects evident only when self-other overlap is high. This research reveals how recipient roles and narrative strategies shape public participation in online charitable projects, providing actionable insights for organizations to craft more effective fundraising messages.</p>