Online communities are valuable tools for information exchange, professional networking, and peer support for health professionals. However, evidence of how and why health professionals are engaging with their peers online is lacking. This study aimed to identify the types and frequency of peer online interactions conducted by health professionals across a broad range of online platforms and identify factors influencing their use. We used online questionnaires to capture health professionals’ online behaviours, digital competency, feelings of online social connectedness, and well-being. Participants (n = 119) used an average of 3.4 platforms. Facebook (66.39%), LinkedIn (64.71%), and WhatsApp (46.22%) were the platforms with the highest account ownership relative to Instagram (45.38%), X (39.50%), YouTube (27.73%), TikTok (14.29%), and Reddit (11.76%). The types of interaction (active vs. passive) health professionals used to engage with their peers varied by platform. A key factor motivating participants to engage in online communities was that our participants possessed the knowledge and skills to leverage the online resources provided by their collective peers for professional benefits. The study revealed a positive association between broader online platform use and greater feelings of social connectedness, while the relationship between social connectedness and well-being was more complex after adjustment for demographic factors. The results of this study highlight the benefits of online peer engagement but also identify strategies that can be implemented to support and enhance the use of online communities for health professionals. Continuing work in this field will enhance understanding of the professional and social benefits provided by online communities for health professionals.