The objectives of the study were a) To compare the body mass index (BMI) of children with the BMI of the international reference of the Center for Disease Control and Prevention (CDC-2012) and b) To investigate if the excess of BMI is related with the performance of the horizontal jump (SH) of children. A descriptive correlational study was carried out. We investigated for convenience 156 children of 6 and 10 years of age (91 men and 65 women) of a Municipal School of Talca (Chile). Age, weight, height and horizontal jump were evaluated. The BMI was calculated and classified into categories of normal weight and excess weight according to the CDC-2012. The average values of the children studied were superior to the CDC-2012 in 1.5kg to 2.5kg in both sexes. Negative and significant relationships between BMI and SH were found in those classified as overweight, ranging from men (r = - 0.15 to -0.64) and in women (r = - 0.25 to -0.24). The children presented higher levels of BMI in relation to the reference of the CDC-2012. This significant increase in adiposity is negatively related to the performance of SH of children, especially when they are classified as having excess body weight.