This study examined the effects of fathers' play participation on young children's social competence and self-regulation. The subjects consisted of 180 fathers with children at ages between 4-7 years old from 2 preschools and 3 kindergartens located in Y city in Gyeonggi province. The analyses used for this study included the t-test and multiple regression analysis. The main findings are as follows. First, fathers' play participation was not different by sociodemographic characteristics such as fathers' age, educational level, and job. Second, fathers' participation in functional play, role play, and constructive play was positively related to social activator, reassurance, and cooperation among subscales on children's social competence. Also, fathers' participation in games was negatively related to reassurance among children and positively related to hypersensitivity among children. Third, fathers' participation in role play and functional play was positively related to children's self-monitoring and self-control. These findings suggest emphasizing fathers' play participation to improve children's social competence and children's self-regulation, and it can be helpful to underline fathers' education and to develop programs for fathers' play.