Objectives: As infants spend extensive time in caregiving and educational institutions, there is a heightened emphasis on the significance of prosocial behavior in cultivating positive relationships. Consequently, this study explores the effects of mothers’ parenting stress on preschoolers' prosocial behavior, with a focus on the mediating effect of mothers’ emotion socialization and preschoolers' effortful control.Methods: A total of 215 mothers of children aged 3-5 years were included in this study. For data analysis, descriptive statistics and path analyses were conducted.Results: First, mothers’ parenting stress did not directly affect preschoolers’ prosocial behavior. Second, mothers’ parenting stress significantly affected preschoolers’ prosocial behavior, mediated by supportive emotion socialization. However, the unsupportive response of emotion socialization did not mediate the relationship between mothers’ parenting stress and preschoolers’ prosocial behavior. Third, mothers’ parenting stress significantly affected preschoolers’ prosocial behavior, mediated by preschoolers’ effortful control. Finally, the serial mediating effect of mothers’ parenting stress on preschoolers’ prosocial behavior, mediated by mothers’ emotion socialization and preschoolers’ effortful control, was significant.Conclusion: The results show that positive parenting aspects such as mothers’ supportive responses (rather than unsupportive responses) and preschoolers’ effortful control have an positive influence on preschoolers’ prosocial behavior. This finding underscores the necessity for targeted intervention programs to mitigate mothers’ parenting stress and enhancing supportive responses to improved prosocial behavior in preschoolers.