Whereas numerous studies have investigated the relationship of cardiorespiratory fitness with inhibition and neuroelectric activity, the role of other physical fitness components and physical activity (PA) intensities in this relationship remain unclear, especially in children with obesity. Therefore, the purpose of this study was to investigate the association of physical fitness, PA, and sedentary time with inhibitory control and neuroelectric activity in children. Eighty-four children (8-11 years) with overweight or obesity performed the ALPHA battery to assess their physical fitness components (i.e., muscular strength, speed-agility, and cardiorespiratory fitness). PA and sedentary time were assessed from hip and nondominant wrist-worn accelerometers. Inhibitory control was evaluated using a flanker task, and expressed as reaction time (RT) and response accuracy. P3 amplitude and latency were recorded using electroencephalography. Higher speed-agility and cardiorespiratory fitness were associated with shorter RT and larger P3 amplitude on incongruent trials. Higher speed-agility was associated with shorter RT on congruent trials. Hip-assessed moderate and moderate-to-vigorous PA were associated with longer P3 latency across trials, and vigorous PA with larger P3 amplitude on incongruent trials. Our results provide initial evidence suggesting that not only cardiorespiratory fitness, but also speed-agility, are associated with inhibitory control and P3 amplitude, whereas no significant associations were observed for muscular strength. The associations between PA (moderate, vigorous and moderate to-vigorous) and neuroelectric activity were accelerometer location-dependent. Promoting PA programs that enhance the cardiorespiratory fitness and speed-agility will contribute to better understanding whether such health improvements benefit inhibitory control in youth with overweight or obesity.