Background: The purpose of this study was to evaluate the feasibility and effectiveness of a high-intensity semisupervised exercise program alongside lifestyle counseling as an intervention for managing cardiometabolic risk in sedentary adults. Methods: A 40-week 3-arm randomized controlled clinical trial (16-wk intervention and 24-wk follow-up) was used. Seventy-five sedentary adults (34–55 y) with at least 1 cardiometabolic risk factor were randomized into one of the following arms: (1) aerobic interval training (AIT) plus lifestyle counseling (n = 25), (2) low- to moderate-intensity continuous training plus lifestyle counseling (traditional continuous training, TCT) (n = 27), or (3) lifestyle counseling alone (COU) (n = 23). Metabolic syndrome severity scores, accelerometer-based physical activity, and self-reported dietary habits were assessed at baseline, after the intervention, and at follow-up. Results: AIT was well accepted with high enjoyment scores. All groups showed similar improvements in metabolic syndrome severity scores (standardized effect size = 0.46) and dietary habits (standardized effect size = 0.30). Moderate to vigorous physical activity increased in all study groups, with the number of responders higher in AIT and TCT groups (50%) than in COU group (21%). Both AIT and TCT had a greater impact on sedentary behavior than COU (63.5% vs 30.4% responders). Conclusions: AIT appears to be a feasible and effective strategy in sedentary individuals with cardiometabolic risk factors. AIT could be included in intervention programs tackling unhealthy lifestyles.