This study aimed to investigate whether the parenting stress of mothers exerts a mediating effect on the relationship between the adult attachment of mothers and emotional regulation of infants. In this study, the adult attachment of mothers was measured using ECRR-K, which is a measure translated and modified by Kim Sung-hyun (2004) , whereas the parenting stress of mothers was determined using a measure modified by Kong Tae-ri (2017). Moreover, the emotional regulation of infants was evaluated using the modified by Park Ye-rang (2017). Data analysis was conducted in accordance with the characteristics and objective of the study. Further, correlation, multiple regression, and hierarchical multiple regression analyses were performed. First, the study found that the relationship among the adult attachment of mothers, parenting stress of mothers, and the emotional regulation of infants was significant. Second, the relationship between the adult attachment of mothers, parenting stress of mothers, and the emotional regulation of infants exerted a significant impact on one another. Lastly, the parenting stress of mothers partially mediated the relationship between the adult attachment of mothers and the emotional regulation of infants. These findings are valuable because they can be used as meaningful data for improving emotional regulation among infants and as a basis for acquiring appropriate parenting skills by identifying the importance of the adult attachment and parenting stress of mothers.