This study examined undergraduates' health information needs, information seeking behaviors, and their perceptions of credibility of health information in social media environments. Interviews with 22 undergraduates revealed that social media was used mainly in a preventive stage or in a health maintenance stage. The perceptions of credibility of health information widely differed according to the type of social media. This finding indicated the need for health information literacy education that could help undergraduates effectively evaluate and acquire health information online.