The aim of this study was to determine the effect of cognitive interference by using the Dual-Task (DT) paradigm on gait parameters according to sex, and age. Additionally, we aim to explore the relationship between Dual-Task-Cost (DTC), physical fitness, cognitive functioning, and weight status in schoolchildren. One hundred schoolchildren participated in this study (age = 8.83 ± 1.82 years). They were randomly assigned to Comfortable Linear Gait (CLG: gait in a straight path) or Complex Gait (CG: gait over obstacles) with and without interference. For CLG, boys and girls showed a reduction in gait speed (