The current study was carried out to determine the mathematical development levels of children attending to a preschool education institution in terms of mathematical content. The research was conducted on 334 children between 60-72 months attending to an independent kindergarten. The mathematical development level of children was measured through Progress in Math 6 Test. As a result of the statistics obtained, it was found that the success of the children for ?Shapes-Space-Measurements? and ?Data Analysis? categories were high in terms of the mathematical development levels of the children, while their success rates were lower than expected in the sub-group of processes at the ?Numbers? category.