ObjectiveThe aim of this study was to compare muscle strength, balance, and physical activity between children with chronic ankle instability and copers. DesignCross-sectional study. SettingPediatric Physical Therapy laboratory. ParticipantsChildren aged between 7 and 12 years old from regular schools who had a history of unilateral ankle sprain. Main outcome measuresLower extremity strength, Static and dynamic standing balance, and Level of physical activity. ResultsFifteen children with chronic ankle instability and 15 copers were recruited. Demographic data showed no differences between group except for sex and the Cumberland Ankle Instability Tool-Youth (CAITY) score. Children with CAI had a significantly lower score during the standing long jump test (p < 0.05), poorer performance of single leg stance test (p < 0.001) and Y-Balance test in the anterior, posteromedial, and posterolateral directions (p < 0.05) when compared to copers. Total METs per week was significantly higher in the copers (p < 0.05). ConclusionChildren with chronic ankle instability exhibited weaker lower limb strength, poorer static and dynamic standing balance, and participate in less physical activity compared to those in a coper group which may have future negative health consequences. Knowledge about the differences between the two groups may provide guidance for physical educators and physical therapists. (200 words)