This study examined (i) the relationship between Body Mass Index (“BMI”) and cognitive performance (inhibitory control) at baseline, and (ii) cognitive changes experienced by lean and overweight-obese children following short bouts of exergaming play. Study participants included 44 children ages 8-12. Each child took cognitive tests before and after playing games in Shape Up (via the Kinect sensor on an Xbox One console), and wore two ActiGraph activity monitors and a Polar heart rate monitor. At baseline, higher BMI percentile was significantly correlated with slower reaction time in total conditions, Word condition, and Interference condition, but was not correlated with response accuracy. Lean and overweight-obese children played a similar amount of games with similar intensity and duration. Post-play, obese-overweight children showed much bigger improvements than their lean counterparts. This was probably due to the fact that they had more room for improvement. Since regular and intense physical activities have a positive impact on cognitive improvement, long-term exergaming interventions are needed to maximize the physical activity effect on children’s obesity and their cognitive development.