The increasing number of studies on the STEM approach necessitates a holistic and comparative evaluation of the results. This study aims to investigate and evaluate the cumulative results of the experimental studies used STEM approach for preschool children. In this study, the meta-analysis method was used. Despite a great number of studies about STEM education, only a limited number of studies were accessed by the keywords "preschool", "early childhood" and "experimental study". The effect size obtained (0.556) is at a level that can be considered as moderate according to the classification used in meta-analysis studies. STEM studies aimed at preschool children have positive effects on children's learning and development. However, more experimental studies on STEM in the preschool field are needed. It can be suggested that preschool teachers can be encouraged to design and implement STEM practices in their class. For further research, the results of the meta-analysis can be supported by content analysis, and a similar study can be conducted for the other grade levels.