On HIV blogs, people living with HIV share their intimate thoughts and experiences with the world in the form of personal online diaries. While previous research investigated the reasons why patients engage in blogging activities, the effects of such diaries on nondiseased recipients are largely unexplored. Following an experimental design, this study (n = 261) tested whether a one-time exposure to a personal HIV blog has greater persuasive effects on its readers than an institutional HIV website providing the same content. Results showed that although source credibility was perceived as higher when reading the HIV website from an official institution, blog readers had more positive attitudes and a higher self-efficacy toward condom use than website readers. Implications for health message design are discussed.