Parenting has a prominent role in predicting children's externalizing behaviors (EB). Although parenting behavior has been shown by prior research to mediate the relationship between parenting self-efficacy (PSE) as the cognitive aspect of parenting and child EB, the role of children's cognitive aspects in the relationship is not yet well understood. To improve understanding of the relationship between PSE, children's EB, and children's cognitive aspect, the current study aims to investigate the mediating effect of children's executive function (EF) on the relationship between PSE and children's EB in early childhood. Questionnaire data on PSE, child EF, and child EB were collected from 217 mothers of typically developed children aged 3 years to 8 years in Indonesia. Hayes PROCESS analysis revealed an indirect effect of maternal PSE on child EB that is mediated by child EF when socioeconomic status is controlled. With this indirect effect accounted for, the direct effect of maternal PSE on child EB disappears, suggesting a full mediation effect. Specifically, the relationship between PSE and child EB is fully mediated by inhibitory control, but only partially mediated by working memory. The discovery indicates that children's EF deficit may increase child EB, along with a decrease in maternal PSE. These findings imply that in providing EB intervention for children, it is necessary to consider PSE and children's EF.