Personal pronouns are vital in language processing and social interaction. Accumulating evidence indicates that the second-person pronoun "you" yields more favorable outcomes than first- (e.g., "I") or third-person pronouns (e.g., "he/she"), as well as non-pronominal phrasing, by enhancing persuasive impact and fostering perspective-taking during narrative comprehension. However, the specific effects and underlying mechanisms of "you" across different domains remain unclear. This systematic review synthesizes 66 articles (screened from 3771 articles) on "you" effects in information persuasion, dyadic communication, and narrative comprehension following the PRISMA guidelines. The key findings are: (1) "You" has a small positive effect in information persuasion (r = 0.10) and narrative comprehension (r = 0.15; bias-corrected estimate), but a small negative effect in dyadic communication (r = -0.15); (2) Contextual and individual characteristics moderate these effects; and (3) "You" effect in each domain has both unique and shared mediators, with the shared ones involving self-relevant attention, mental simulation, and psychological distance. Integrating these findings, we propose a model that offers a more comprehensive explanation of how "you" works across different domains.