The purpose of this research was to examine the extent to which preschools satisfy the natural need for physical activity of a young child in the summer holidays and during the school year. The measurement of physical activity of children and its level was performed with the use of Actigraph accelerometers and the Steps per Minute test. The sample comprised children (N = 414) aged 4-6 who attended selected preschools in Poland. The Mann-Whitney U test and Kruskal-Wallis test were used to determine statistical differences between the levels of physical activity. Significant differences in physical activity of children in preschools during the summer holidays and the school year were observed. The results of this study showed that the level of physical activity of children during their stay in preschool is not optimal, which, in turn, may be a limiting factor for their overall development.