The purpose of this study was to assess the physical activity of preschool children during free play, using accelerometry and direct observation methods. Accelerometry is increasingly being used to objectively assess physical activity in children. Direct observation is often considered a criterion measure for physical activity in young children because of its practical and comprehensive nature. In this study, the participants were 6 preschool children aged 5-6 years. Children's physical activity levels (intensities) during free play (30 minutes) in the kindergarten were measured by the triaxial accelerometer (HJA-350IT ; Omron). These time series data were time-matched with behaviors and/or movement patterns from the video footage of children engaging in free play. Thus, we tried to indicate the physical activity levels of children during various activities and/or fundamental movements. Results were as follows. 1) Skilled children were more active and performed more high-intensity physical activity than unskilled children did during free-play periods. The amount and intensity of physical activity was much lower in unskilled girls than in other children. 2) More types of activities and/or fundamental movements were performed by skilled children than by unskilled children. 3) Movement intensity of children during free-play activities was adequately classified. Based on these findings, a cut-off point of moderate-to-vigorous physical activity was determined.