Online social networks (OSNs) enable health professionals to learn informally, for example by sharing medical knowledge, or discussing practice management challenges and clinical issues. Understanding how learning occurs in OSNs is necessary to better support this type of learning. Through a cross-sectional survey, this study found that learning interaction in OSNs is low in general, with a small number of active users. Some health professionals actively used OSNs to support their practice, including sharing practical and experiential knowledge, benchmarking themselves, and to keep up-to-date on policy, advanced information and news in the field. These health professionals had an overall positive learning experience in OSNs.