BackgroundPhysical activity in natural environments, such as trail running, is a way to nurture physical and mental health. However, running has an inherent risk of musculoskeletal injuries. ObjectivesTo investigate the prevalence of running-related injuries (RRI) and cramps, and to describe the personal and training characteristics of Brazilian trail runners. MethodsA total of 1068 trail runners were included in this observational cross-sectional study. The participants had at least six months of trail running experience. The data were collected between April 2019 and February 2020 through an online and self-reported survey. ResultsThe point prevalence of RRIs was 39.2 % (95 % credible interval [CrI]: 36.3, 42.1). The body region with the highest point prevalence was the knee. The 12-month period prevalence of RRIs was 69.2 % (95 %CrI: 66.4, 72.0). The body region with the highest 12-month period prevalence was the lower leg. 1- and 12-month period prevalence of cramps was 19.5 % (95 %CrI: 17.1, 21.9) and 36.0 % (95 %CrI: 33.0, 38.8), respectively. Triceps surae was the muscle most affected by cramps. ConclusionsTwo in 5 (40 %) trail runners reported being injured at the time of data collection, and about 2 of 3 reported previous RRIs in the last 12 months. The most prevalent injured body regions were the knee and the lower leg. One in 5 trail runners reported cramps in the last month, increasing to 36 % in the last 12 months. Knowing better the characteristics of the population and the burden of health conditions may inform better decisions regarding implementation actions toward trail running practice.