This study examined the structural relationships among parent’s play participation, children’s playfulness, selfregulation and happiness. In this Study, subjects were 274 children who were 4 through 5 years old. The participants included 274 preschoolers’ parents and their teachers in D city. The parents completed questionnaires regarding parent’s play participation with their children and children’s self-regulation. The teachers completed questionnaires regarding preschoolers’ happiness and playfulness. Data was analyzed using descriptive statistics, pearson correlation analysis and mediation analysis based on structural equation modeling with SPSS 25.0 and AMOS 23.0 program. Also, specific indirect effects were analyzed using AMOS user-defined estimand function. The primary results of this study were as follows. 1) The parent’s play participation had an influence upon children’s playfulness and self-regulation. 2) The children’s playfulness had an influence upon children’s self-regulation and happiness. 3) The children’s self-regulation had an influence upon children’s happiness. 4) Between the parent’s play participation and children’s happiness were mediated by the children’s playfulness and self-regulation. This study revealed that parent’s play participation, children’s playfulness and self-regulation need to be considered simultaneously to explain the level of the children’s happiness. The results highlight the structural relationships among parent’s play participation, children’s playfulness, self-regulation and happiness.