Background Due to recent treatment advances, people who have non-small cell lung cancer with oncogenic alterations are an important new group of cancer survivors. Little is known about lung cancer online support communities. This research was guided by two primary questions: (1) How do these lung cancer survivors engage in online support communities? and (2) What are the psychological, social, and physical impacts of such engagement? Methods Qualitative in-depth interviews were conducted with patients with advanced lung cancer (N = 40) to learn about their experiences with the illness. We used qualitative thematic analysis, inductive and deductive, as outlined by Carspecken. We adapted the framework for studying online communities developed by Zhang and colleagues to examine engagement with and impacts of involvement in online lung cancer support communities. Results Participants described engaging in the online community through (1) initializing communication through asking questions or sharing resources, (2) responding to others comments or inquiries, or (3) simply observing/reading others posts. Participation had physical, psychological, or social impacts, with benefits (e.g., empowerment) and risks (e.g., feelings of jealousy or misinformation) in each domain. Participants used various strategies to mitigate negative impacts, such as distancing oneself as needed. Conclusions Online lung cancer support communities provide support, camaraderie, and specialized health information. However, there are also risks of online engagement, such as social comparison or accessing misinformation. Understanding the utility of online support communities for lung cancer survivors on targeted therapies and further addressing their risks are urgent tasks, especially in the post-COVID era.