The purpose of this study was to examine associations of fundamental movement skills (FMS) with measures of body composition among children and adolescents. Secondary analyses of cross-sectional data collected from 4,363 children and adolescents in Grades 4, 6, 8, and 10 as part of the 1997 New South Wales Schools Fitness and Physical Activity Survey were conducted. Six FMS (run, vertical jump, throw, catch, kick, and strike) were assessed by observation. Height and weight (used to calculate body mass index; BMI) and waist circumference were directly measured. Results indicated that the children's and adolescents' ability to perform FMS was significantly related to BMI and waist circumference. Specifically, BMI and waist circumference were significant predictors for FMS in six of the eight demographic groups. Adjusted odds ratios revealed that overweight boys and girls in all grades were less likely to possess high levels of FMS and more likely to possess low levels of FMS than those who weren't overweight. When FMS were partitioned into locomotor and object-control skills, nonoverweight boys and girls in each grade were two to three times more likely to possess more advanced locomotor skills than overweight boys and girls. However, for object-control skills, the only demographic groups in which nonoverweight students possessed a greater number of advanced skills than overweight students were boys in Grades 6 and 10. There appear to be significant and important associations between performance of locomotor skills and weight status among children and adolescents. This would suggest that intervention strategies to prevent unhealthy weight gain among children and youth might usefully include increasing proficiency of locomotor skills as a key component.