Obj e c t i v e : The purpose of this study is to verify the longitudinal effects of mothers’ parenting behavior in infancy on the school adjustment of 1st graders in elementary school and to analyze whether early childhood school readiness mediated the relationship between them. Methods: This study, using Korean Children’s Panel Survey, targeted children in 841 households. SPSS 25.0 was used to analyze differences among major variables and Pearson’s correlation. The mediating effect of school readiness was verified using PROCESS macro 4.1. Results: Both subfactors of mother’s parenting behavior were related to school adjustment. In other words, the mother’s compassionate parenting behavior directly affected school adjustment and the con- trolled parenting behavior indirectly affected children’s school adjustment mediated by school readiness. Conc lus i ons: The results of this study suggest that both sub-factors of mothers' parent- ing behavior should be encouraged from infancy for children's positive school adjustment. Additionally, this study shows that school preparation guidance is necessary for preschool chil- dren to successfully adapt to school.