This study was conducted to investigate the immediate impacts of preschool attendance on Turkish children's mathematics achievement. The participants were 200 children who attended or did not attend preschool. The number and operation task and the geometric shapes sorting task were used as the data collection tools. The children who attended preschool performed significantly better on the number and operation task and the geometric shapes sorting task than the children who did not attend preschool. Indeed, the multivariate regression analysis demonstrated that preschool attendance is the most important predictor of the success of children in number and operation task and the geometric shapes sorting task.