Previous studies found that physicians working in developed countries in Europe and in the USA declared insufficient knowledge concerning immune-related adverse events (irAE) following use of immune checkpoint inhibitors (ICI) in cancer treatment. We determined this knowledge gap among rheumatologists and medical students (MS) in Brazil. A web-based structured survey or a direct interview was applied to 1428 board-certified Brazilian rheumatologists and an adapted questionnaire was sent to 840 undergraduate MS attending the last 2 years of Medical Schools in Fortaleza-CE, Brazil, in September 2019. 228 (15.9%) rheumatologists and 145 (17.2%) MS answered the survey; 136 (60%) rheumatologists worked at Institutions with Oncology service. Rheumatologists had 22.6 ± 12.6 years of medical practice, most [116 (50.9%)] worked in private practice and 9 (3.9%) were on training. Fifty-three (23.4%) declared being familiar [40 (17.6%)] or very familiar [13 (5.8%)] with irAE. Almost two-thirds declared having never managed irAE and about a third (38.6%) felt confident in managing such patients. Knowledge among rheumatologists was similar regardless of having more or less than 10 years of practice (P = 0.758). Less than 5% MS declared being familiar with ICI and most have never heard of irAE. There is a large gap concerning knowledge about ICI and irAE among rheumatologists and MS in Brazil. Continuing medical education strategies are needed to improve this knowledge.