ABSTRACT Background Adolescence is a critical time for establishing behaviors. 24-hour movement behaviors, including physical activity, sleep, and sedentary time, are likely to influence obesity, cardiovascular, and cognitive health. The aim was to examine associations between 24-hr movement behaviors, cardiometabolic health and cognitive functions in adolescents with and without obesity. Methods This was a cross-sectional study that included adolescents (n = 30, ages 12–16) with obesity and normal weight controls matched on age and sex. 24-hr movement behaviors of physical activity, sedentary time, and sleep were assessed using waist-worn accelerometers. Cardiometabolic health was measured using flow-mediated dilation (FMD) in the brachial artery, body composition via dual x-ray absorptiometry, blood pressure, and blood analyses of cholesterol, glucose, and insulin. Cognitive health was assessed using two computer-based tasks. Linear regressions were used to examine associations between 24-hr movement behaviors, cardiometabolic health, and cognition. Results In examining relationships between 24-hr movement behaviors and cardiometabolic health, when adjusted for body fat percentage, MVPA was positively associated with cardiovascular health (FMD log difference 0.1, 95%CI: 0.003, 95%CI: .001, .01, p = .020), sedentary time was negatively associated (−0.7, 95%CI: −1.3, −0.2, p = .016), and total sleep time was negatively associated with HDL cholesterol (−0.1, 95%CI: −0.2, −0.005, p = .039). There were no statistically significant associations between 24-hr movement behaviors and cognitive outcomes, except sleep and reactive control. When examining relationships between cardiometabolic and cognitive outcomes, higher HDL was associated with improved cognitive accuracy and higher insulin was associated with slower reaction times. Conclusions 24-hour movement behaviors of MVPA, sedentary time, and sleep time were associated with cardiometabolic measurements in a small sample. 24-hr movement behaviors, particularly MVPA and sedentary time, may be important behaviors for cardiometabolic health in adolescents, independent of body composition. Additional research is needed on the triadic relationship between 24-hr movement behaviors, cardiometabolic health, and cognitive performance.