This study examined postural sway in children in eyes open (EO) and eyes closed (EC) conditions, controlling for body mass index (BMI) and physical activity (PA). Sixty two children (aged 8–11years) underwent sway assessment using computerized posturography from which 95% ellipse sway area, anterior/posterior (AP) sway, medial/lateral (ML) sway displacement and sway velocity were assessed. Six trials were performed alternatively in EO and EC. BMI (kg/m2) was determined from height and mass. PA was determined using sealed pedometry. AP amplitude (p = .038), ML amplitude (p = .001), 95% ellipse (p = .0001), and sway velocity (p = .012) were higher in EC compared with EO conditions. BMI and PA were not significant as covariates. None of the sway variables were significantly related to PA. However, sway velocity during EO (p = .0001) and EC (p = .0001) was significantly related to BMI. These results indicate that sway is poorer when vision is removed, that BMI influences sway velocity, but that pedometer-assessed PA was not associated with postural sway.