This study aims to examine which variables influence children’s personality most strongly by verifying a structural relationship among children’s personality, children’s temperament, parenting attitude, and peer competence. This study selected parents and classroom teachers whose children aged 5 attended an early childhood education institute. This study distributed two questionnaires to teachers and parents, that for the parents about their children’s temperament and parenting attitude and that for the teachers about children’s personality and peer competence. The collected data were statistically analyzed with SPSS 21.0 and AMOS 21.0. This study adopted SEM (Structural Equation Modeling) analysis to verify the children’s personality and its variables and the Sobel test to verify the mediating effect of measurement variables. As a result, children’s temperament, parenting attitude, and peer competence were found to have a direct effect on children’s personality. Moreover, children’s temperament had an indirect effect on their personality, mediated by parenting attitude and peer competence. In particular, peer competence affects children’s personality most, followed by parenting attitude and children’s temperament. It is expected that the results of this study will help us to better understand children’s personality and serve as basic data for the development of children personality education programs in the near future.