The main purpose of the study was to define optimal criterion-referenced cut-points for cardiorespiratory fitness (CRF) associated with overweight/obesity. In this cross-sectional study, participants were 1,612 children aged 7–14?years (mean age?±?SD?=?9.7?±?2.4?years; 52.5% girls). CRF was assessed by the Maximal multistage 20-m shuttle run test, from which maximal oxygen uptake (VO2max) was estimated. Anthropometric indices included body-mass index (BMI), waist circumference (WC), and waist-to-height ratio (WHtR). Receiver operating characteristic (ROC) curves were performed to determine cut-off points. In boys, the optimal cut-off points of CRF in defining overweight/obesity for BMI, WC, and WHtR were 44.6, 46.4, and 46.9?mlO2/kg/min. The areas under the curves (AUC) were 0.83 (95% CI 0.78–0.88, p?<?0.001), 0.77 (95% CI 0.71–0.83, p?<?0.001), and 0.90 (95% CI 0.86–0.93, p?<?0.001). In girls, the optimal cut-off points were 41.0, 40.8, and 40.7?mlO2/kg/min for BMI, WC, and WHtR, with the AUCs of 0.86 (95% CI 0.82–0.90, p?<?0.001), 0.83 (95% CI 0.79–0.88), and 0.88 (95% CI 0.84–0.93, p?<?0.001). In conclusion, our newly developed cut-off points for CRF assessed by the Maximal multistage 20-m shuttle run test may adequately detect primary school-aged boys and girls with general and abdominal obesity.