The study of the transformation of personal epistemology in young children, as a research vacuum, has attracted the attention of specialists in recent years. The results of studies show that the transformation of beliefs in childhood can be studied in conjunction with the theory of mind. the purpose of this study was to investigate the evolution of beliefs in relation to the theory of mind and executive function in preschool children. The research method is cross-sectional. To this end, 110 children aged 6 years old were selected by available sampling method from preschools in Tehran For each child, two ideas of false beliefs (Weimer and Perner, 1983; Perner, Lickman, and Wimmer, 1987), . Two personal epistemology assignments (Bohr and Huffer, 2002) and the Wisconsin Card Classification test were considered Findings: There is a significant positive relationship between personal epistemology, theory of mind and executive function. Also, the results of regression analysis showed that personal epistemology is predictable through the theory of mind and executive functions Accordingly, in the first step, approximately 56% of the variance of personal epistemology was explained through the theory of mind. . In the second step, theory of mind and executive functions explained %73 of the variance in personal epistemology. Therefore, the coefficient of determination increased from %56 to %73 as the variable entered executive functions into the analysis.