The present study examined the associations of physical fitness and motorcompetence with P3 and alpha desynchronization (ERD), two neuroelectric indices ofbrain development underlying controlled attention, in 4-6 year-old preschool children. Allparticipants completed physical fitness and motor competence test batteries and anauditory oddball task while electroencephalogram (EEG) was recorded. Resultsrevealed that increased muscular power, muscular endurance, physical fitness, andmotor competence were associated better attentional task performance. Analysis onneuroelectric indices showed that muscular endurance was related to increased P3amplitude, while the increases in physical fitness and motor competence wereassociated with greater upper alpha (10-12 Hz) ERD following the stimulus evaluationand response selection. Further, the negative associations of physical fitness and motorcompetence with task response time were mediated by the upper alpha ERD. Thesefindings highlight the importance of early childhood motor competence and physicalfitness, especially muscular endurance, to neurocognitive function.