Patients with cancer considering immune checkpoint inhibitor (ICI) therapy often look for health information and peer support through online communities. The authors used social media content analysis to obtain the perspectives of patients receiving ICI treatment about immune-related adverse events (irAEs), with particular focus on rheumatological symptoms. The most reported rheumatic symptom was joint pain. Other commonly reported symptoms included muscle pain, joint stiffness, arthritis, myositis, bone pain, back pain, and tendon/ligament pain. A few users reported development of rheumatic diseases. The authors' analyses allowed for cataloging and assessment of patient and caregiver experiences with ICI therapy and rheumatic irAEs.