In this study, it is aimed to examine the effect of augmented reality application on preschool children's knowledge of space. A mixed method, which combines both quantitative and qualitative methods, was used in the study. The study group consists of 24 children aged 60-72 months. In the study, a 10-question form created in line with the opinions of experts in the field of pre-school and science education was used to measure preschool children's knowledge of space. Children's views on the augmented reality practice were determined through semi-structured interviews. Space-themed augmented reality card set for teaching space in the experimental group; in the control group, 2D visuals were used. Obtained data were analyzed using Mann Whitney U test and Wilcoxon test. In the study, it was found that the knowledge levels of the children in the experimental and control groups before the application were close to each other; as a result of the trainings made with the augmented reality application, it was seen that the level of knowledge increased in favor of the experimental group. As a result of the interviews with the children, it was determined that the augmented reality practice drew more attention of the children, created a greater sense of reality, and got them excited compared to the practice with two-dimensional visuals. It has been observed that there are not many studies on supporting preschool children's knowledge of space with technological tools. In this context, it is thought that the study will shed light on the literature.