Abstract Background It is currently unknown whether patients with childhood-onset Takayasu disease (c-TA) are prone to physical inactivity and poor aerobic capacity. In this study, we assessed physical activity levels and cardiorespiratory fitness along with health-related quality of life (HRQL) and various traditional and non-traditional risk factors in patients with c-TA vs. healthy controls. Methods c-TA patients with non-active disease (n = 17) and age- and sex-matched healthy controls (n = 17) were enrolled in the study. We assessed physical activity levels, aerobic capacity, body composition, systemic inflammation, cardiometabolic markers, disease-related parameters, and HRQL. Results c-TA patients showed greater time spent in sedentary behavior (P = 0.010), and lower moderate-to-vigorous physical activity (P > 0.001) and lower step counts per day (P > 0.001). VO_2peak (P < 0.001) and chronotropic response (P = 0.016) were significantly lower in patients with c-TA and they had worse HRQL in physical domain (P < 0.001), lower bone mineral content and density, and higher insulin levels vs. healthy controls (all P ≤ 0.05). Conclusions c-TA patients exhibited reduced physical activity levels and aerobic capacity, worse cardiometabolic risk factors and HRQL parameter compared with healthy peers. Physical inactivity and aerobic deconditioning emerge as potentially novel risk factors for c-TA. The role of physical activity interventions in preventing poor outcomes and improving HRQL in c-TA remains to be explored.