Background: Social media is frequently used by consumers and health care professionals; however, our knowledge about its use in a professional capacity by pharmacists is limited. Objective: Our aim was to investigate the professional use of social media by pharmacists. Methods: In-depth semistructured interviews were conducted with practicing pharmacists (N=31) from nine countries. Interviews were recorded, transcribed verbatim, and thematically analyzed. Results: Wikipedia, YouTube, and Facebook were the main social media platforms used. Professional use of social media included networking with peers, discussion of health and professional topics, accessing and sharing health and professional information, job searching, and professional promotion. Wikipedia was the participants’ first choice when seeking information about unfamiliar topics, or topics that were difficult to search for. Very few pharmacy-related contributions to Wikipedia were reported. YouTube, a video-sharing platform, was used for self-education. University lectures, “how-to” footage, and professionally made videos were commonly watched. No professional contribution was made to YouTube. Facebook, a general social networking site, was used for professional networking, promotion of achievements, and job advertisements. It also afforded engagement in professional discussions and information sharing among peers. Conclusions: Participants used social media in a professional capacity, specifically for accessing and sharing health and professional information among peers. Pharmacists, as medicines experts, should take a leading role in contributing to health information dissemination in these user-friendly virtual environments, to reach not only other health care professionals but also health consumers. J Med Internet Res 2016;18(9):e258 doi:10.2196/jmir.5702