Physical fitness is one of the important health markers as a predictor of cardiovascular disease mor-bidity and mortality. Objectives: To evaluate the relationship between fat mass with anthropome-tric indicators and, secondly, to compare the performance of physical fitness among children and adolescents categorized with adequate and excess fat mass. Subjects and Method: A descriptive cross-sectional study was conducted with 863 schoolchildren aged 6 to 17.9 years. Weight, height, and waist circumference were measured. physical fitness [speed (20m), agility (10x5m), and horizontal jump] was evaluated. Fat mass was calculated by anthropometric equation, body mass index, ponderal index, and waist to height ratio. Data were grouped into 6 age groups. Results: Children of both sexes categorized as having adequate levels of fat mass had lower values of body mass index, ponderal index, and waist to height ratio than children with high levels of fat mass. In physical fitness, children with adequate fat mass were better than the ones with elevated fat mass. In girls with adequate fat mass, better results were observed in horizontal jump and agility during adolescence. There were no differences in the speed test. Conclusion: Fat mass can be considered as a valuable tool for determining excess body fat and categorizing children and adolescents with adequate and excess fat mass. In addition, having acceptable levels of fat mass may contribute to better physical fitness in boys in horizontal jump, agility, and speed and, in girls, only in horizontal jump and agility.