Excess body weight and fat mass levels in children have previously been associated with childhood hypertension. The aim of the current study was to identify anthropometric and body composition indices most strongly associated with hypertension and to propose relevant cut-off values for these indices, above which the likelihood of hypertension in schoolchildren aged 9-13 years old is increased. A sample of 2,665 children participated in a cross-sectional epidemiological study, the Healthy Growth Study. The current study enrolled 1,315 children with full data on blood pressure, anthropometric, and body composition indices. Increased blood pressure in children was associated with body mass index (BMI) (odds ratio (OR) 1.188), waist circumference (OR 1.062), waist-to-height ratio (OR 1.101), total body fat mass (OR 1.063), and trunk fat mass levels (OR 1.083). Also, BMI, waist circumference, waist-to-height ratio, trunk fat mass, and total body fat mass levels above the age-specific and gender-specific cut-off values identified in the present study were associated with a higher likelihood of hypertension. Anthropometric and body composition indices and the relevant cut-off values proposed by the current study can be used for identifying children with higher likelihood of presence of hypertension, as the available BMI thresholds for identifying overweight and obese children may underestimate those at increased risk of hypertension. It is essential for future studies to confirm these findings.